Zoology
Other Invertebrates

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Victoria County History

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William Page (editor)

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1906

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121-134

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'Zoology: Other Invertebrates', A History of the County of Somerset: Volume 1 (1906), pp. 121-134. URL: http://british-history.ac.uk/report.aspx?compid=117305 Date accessed: 23 October 2014.


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MYRIAPODA

Although it cannot be claimed that Somerset has been well worked so far as Myriapoda are concerned, since collections have been made at three localities only, it is not likely that further search will do much more than extend our knowledge of the distribution throughout the county of the species recorded in the subjoined list, and add a few species to it. Two or three species not yet obtained certainly await discovery, if their existence in Somerset may be inferred from what has been ascertained of their range in other counties in the south of England. Amongst the missing species which are common elsewhere may be mentioned Lithobius melanops, Polyxenus lagurus, Glomeris marginata, Iulus sabulosus, I. pilosus and I. teutonicus. Setting aside the last-named, about which there is room for doubt, it is safe to prophesy that the species here mentioned will be found as soon as collecting researches have been further extended.

Of the forms already discovered the rarest are unquestionably Lamyctes fulvicornis, Polydesmus inconstans and Blaniulus fuscus. Yet the scarcity or apparent absence of these species in other counties is probably attributable not so much to their rarity as to their having been overlooked or unsought for.

The specimens recorded below from Winsford were collected by Mr. F. C. Woodbridge. Winsford is a small village on the borders of Exmoor. Those from Blue Anchor and Leigh Woods were collected by Mr. R. I. Pocock. Blue Anchor is a small village lying between Watchet and Minehead on the coast of the Bristol Channel. Leigh Woods is situated in the extreme northern part of the county on the southern side of the river Avon, which here constitutes the boundary line between Somerset and Gloucestershire.

Chilopoda Centipedes Lithobiidæ

Short-bodied, swift-running centipedes, furnished with eyes and only fifteen pairs of legs.

1. Lithobius forficatus, Linn. Syst. Nat. ed. 10, p. 638 (1758).

Blue Anchor, Winsford, Leigh Woods.

The common large brown species met with everywhere under stones in gardens and backyards, as well as in fields and woods. Widely distributed in north and central Europe.

2. Lithobius variegatus, Leach. Zool. Misc. iii. 40 (1817).

Blue Anchor, Winsford, Leigh Woods.

This species is of peculiar interest on account of its being confined, so far as is at present known, to the British and Channel Islands. It is as large as the preceding, but may be at once distinguished by the different spinous armature of the legs and its variegated colouring.

3. Lithobius melanops, Newport. Tr. Linn. Soc. xix. 371 (1845).

Blue Anchor, Winsford.

Much resembling the preceding species in colour, but smaller and armed with 2+2 labial teeth.

4. Lithobius calcaratus, C. Koch. Die Myr.Gatt. Lithobius, p. 86 (1862).

Blue Anchor, Winsford.

A smaller and blacker species than the last, with long antennæ and the legs of the last pair modified in the male. Widely distributed in central Europe.

5. Lithobius crassipes, C. Koch. Die Myr.Gatt. Lithobius, p. 71 (1862).

Blue Anchor, Winsford.

Scarcely as large as L. calcaratus, paler and with shorter antennæ; resembling a dwarfed L. forficatus, for the young of which it is frequently mistaken. Commonly distributed throughout central Europe.

6. Lithobius microps, Meinert. Nat. Tidskr. (3), v. 265 (1868).

Blue Anchor.

The smallest of the British species of Lithobius; distinguishable by the small number of eyes on each side of the head.

7.Lamyctes fulvicornis, Meinert. Nat. Tidskr. v. 266 (1868).

Blue Anchor.

This species is no larger than L. microps.

It is widely distributed on the continent, and, although infrequently met with, certainly ranges throughout the south of England. It is a small dark-coloured species, at once distinguishable from the species of Lithobius by the presence of a single eye on each side of the head, etc.

CRYPTOPIDÆ

Eyeless centipedes of medium length, with twenty-one pairs of short legs.

8. Crypt ops hortensis, Leach. Tr. Linn. Soc. Lond. xi. 384 (1815).

Blue Anchor, Winsford.

Widely distributed throughout north and central Europe.

GEOPHILIDÆ

Long vermiform centipedes without eyes and furnished with a large but variable number of legs.

9. Geophilus flavus, De Geer. Mèm. Ins. vii. 561 (1778) (=longicornis, Leach).

Winsford, Blue Anchor, Leigh Woods.

Common throughout Great Britain and north and central Europe. This species is distinguishable by its long and cylindrical antennal segments.

10. Geophilus carpophagus, Leach. Zool. Misc. iii. 43 (1817).

Winsford, Blue Anchor.

Differing from the preceding and the rest of the British species by the 'ball and socket' method of articulation of its anterior sternal plates. Common in western Europe.

11. Geophilus truncorum, Meinert. Nat. Tidskr. iv. 94 (1866).

Blue Anchor.

This small and delicate species, which is widely distributed in the south of England and western Europe, is distinguished by the presence of three deep grooves on the anterior sternal plates.

12. Linotænia crassipes, C. Koch. Deutschl. Crust. etc., pt. 3, pl. 3 (1835).

Leigh Woods.

13. Linotænia acuminata, Leach. Zool. Misc. iii. 45 (1817).

Leigh Woods.

These two nearly allied species or Linotænia are the two common British luminous centipedes which so frequently attract attention on damp evenings in the autumn by the emission of a phosphorescent secretion from their sternal glands. L. crassipes may be distinguished, amongst other characters, from L. acuminata by the deeper emargination of the anterior border of the coxal plate of the poison-jaws.

14. Linotænia maritima, Leach. Zool. Misc. iii. 44 (1817).

Portishead, near Avonmouth.

This species is nearly allied to L. acuminata, but is much larger. It is generally distributed in suitable localities round the shores of Great Britain and the continental coasts of the English Channel and North Sea. It occurs beneath stones between tide-marks or under cast-up seaweed. It was found by Mr. Pocock in vast numbers on a pebbly beach some two miles south of Portishead, under an accumulation of decaying seaweed marking the last high tide.

15. Schendyla nemorensis, C. Koch. Deutschl. Crust. etc. pt. 3, pl. 4 (1837).

Blue Anchor, Winsford.

A small, delicate and widely distributed species, much resembling G. truncorum in size and general appearance.

16.Stigmatogaster subterraneus, Leach. Tr. Linn. Soc. Lond. xi. 385 (1815).

Blue Anchor, Winsford.

Widely distributed in Great Britain and the adjacent countries of Europe. Distinguished from the rest of the British species by its inflated porous anal pleuræ, and large number of segments.

MYRIAPODA DIPLOPODA Millipedes POLYDESMIDÆ

Millipedes in which there are from nineteen to twenty body-segments, most of which are furnished, at least in the British species, with scent pores supported on larger or smaller lateral crests or keels.

17.Polydesmus complanatus, Linn. Faun. Suecic. ed. 2, p. 502 (1761).

Blue Anchor, Winsford.

The commonest and largest British species.

18. Polydesmus inconstans, Latzel. Bull. Soc. Rouen (2), xix. 269 (1883).

Blue Anchor.

A smaller and much scarcer species than the foregoing. Occurs also in the north of France and western Germany.

19. Brachydesmus superus, Latzel. Die Myr. Öst. Ung. Mon. ii. p. 130 (1884).

Blue Anchor.

Widely distributed in England and central Europe. The only species of the genus found in Great Britain. Distinguishable from the species of Polydesmus by possessing only nineteen body segments.

CHORDEUMIDÆ

Millipedes with thirty or thirty-two body segments furnished dorsally with six symmetrically disposed bristles, without pores and usually keeled like those of the Polydesmus.

20. Atractosoma polydesmoides, Leach. Zool. Misc. iii. 36 (1817).

Leigh Woods.

Widely distributed throughout the south of England and on the continent. With its large lateral keels, this species closely resembles an elongated Polydesmus.

IULIDÆ

Cylindrical millipedes with a large but variable number of segments, furnished with repugnatorial pores, but without large lateral plates.

21. Iulus niger, Leach. Zool. Misc. iii. p. 34 (1817).

Blue Anchor.

A large black species with a longish pointed tail and transverse grooves on the anterior portion of the segments. Common throughout England and the western countries of Europe.

22. Iulus ligulifer, Latzel. Berl. Ent. Zeits. xxxvi. 152 (1891).

Blue Anchor, Winsford.

Resembling the last in colour and the presence of a long pointed caudal process, but smaller and hairier and without transverse grooves on the anterior portion of the segments. Scarce in England, but widely distributed in central Europe.

23.Iulus punctatus, Leach. Zool. Misc. iii. 34 (1817).

Blue Anchor, Winsford, Leigh Woods.

A pale-coloured species with a lateral row of darker spots, and a bluntly clavate caudal process. Found in rotten wood. Distributed everywhere throughout central and northern Europe.

24. Iulus britannicus, Verhoeff. Berl. Ent. Zeits. xxxvi. 147 (1891. Winsford.

A small brown species without caudal process. Fairly common in the south of England and western Europe.

25. Iulus pusillus, Leach. Tr. Linn. Soc. xi. 379 (1814). Winsford.

A small black tailless species, with yellow dorsal band. Widely distributed, but not of common occurrence in England and the countries of western and central Europe.

26. Blaniulus guttulatus, Bosc. Bull. Soc. Phil. p. 12 (1792).

Blue Anchor.

A long, slender, eyeless species with the anterior extremity of the body pale and a line of blood-red spots on each side of the body. Widely distributed in Great Britain and central and northern Europe.

27. Blaniulus fuscus, Stein. Jahr, Nat. Les. Graubündens, p. 139 (1857).

Blue Anchor.

Not nearly so common in England as the preceding species, from which it may be at once distinguished by the presence of eyes. Widely distributed in central Europe.

ARACHNIDA

Two small collections only, including thirty-one species, have come to hand from the county of Somerset, one made at Clifton in the Leigh Woods, the other in the suburbs of Bristol, by Messrs. R. I. Pocock and F. P. Smith respectively.

ARANEÆ ARACHNOMORPHÆ DRASSIDÆ

Spiders with eight eyes, situated in two transverse rows. The tracheal openings lie immediately in front of the spinners. The tarsal claws are two in number, but the anterior pair of spinners are set wide apart at their base, and the maxillæ are deeply impressed across the middle.

1. Drassodes lapidosus (Walckenaer).

Leigh Woods (R. I. P.).

2. Prosthesima latreillii, Simon.

Leigh Woods (R. I. P.).

3. Prosthesima pedestris (C. L. Koch).

Leigh Woods (R. I. P.).

PISAURIDÆ

Spiders with eight eyes in three rows, and three tarsal claws. The first row of eyes consists of four small eyes which are sometimes in a straight line, sometimes recurved and sometimes procurved. Those of the other two rows are situated in a rectangle of various proportions. Pisaura runs freely over the herbage, carrying its egg-sac beneath the body.

4. Pisaura mirabilis (Clerck).

Bristol (F. P. S.).

Very common; adult in June and July.

Known also as Dolomedes or Ocyale mirabilis.

LYCOSIDÆ

The members of this family have also eight eyes, similarly situated to those of the Pisauridœ, the tarsal claws also being three in number. The spiders are to be found running freely and carrying their egg-sac attached to the spinners. Many of the larger species make a short burrow in the soil and there keep guard over the egg-sac.

5. Lycosa ruricola (De Geer).

Leigh Woods (R. I. P.).

6. Lycosa pulverulenta (Clerck).

Leigh Woods (R. I. P.).

7. Pardosa amentata (Clerck).

Bristol (F. P. S.).

AGELENIDÆ

Spiders with eight eyes, situated in two transverse rows. Legs with three tarsal claws. The species of this family spin a large sheet-like web, and construct a tubular retreat at the back of it, which leads to some crevice amongst the rocks or the herbage or the chinks in the walls of outhouses, wherever the various species may happen to be found. The posterior pair of spinners is usually much longer than the other two pairs.

8. Tegenaria silvestris, L. Koch.

Leigh Woods (R. I. P.).

9. Tegenaria atrica, C. L. Koch.

Leigh Woods (R. I. P.).

10. Cœlotes atropos (Walckenaer).

Leigh Woods (R. I. P.).

ARGIOPIDÆ

The spiders included in this family have eight eyes, situated in two rows, the lateral eyes of both rows being usually adjacent, if not in actual contact, while the central eyes form a quadrangle. The tarsal claws are three, often with other supernumerary claws. The web is either an orbicular (wheel-like) snare, or consists of a sheet of webbing beneath which the spiders hang and capture the prey as it falls upon the sheet.

11. Araneus diadematus (Clerck). Leigh Woods (R. I. P.).

12. Meta segmentata (Clerck). Leigh Woods (R. I. P.); Bristol (F. P. S.).

13. Zilla x -notata (Clerck).

Bristol (F. P. S.).

14. Zilla atrica, C. L. Koch. Leigh Woods (R. I. P.).

15. Lepthyphantes tenuis (Blackwall). Leigh Woods (R. I. P.).

16. Bathyphantes concolor (Wider). Leigh Woods (R. I. P.).

17. Linyphia triangularis (Clerck). Leigh Woods (R. I. P.).

18. Macrargus abnormis (Blackwall). Leigh Woods (R. I. P.).

19. Gonatium rubens (Blackwall) Bristol (F. P. S.).

THERIDIIDÆ

The members of this family have eight eyes situated very much like those of the Argiopidæ;, but the mandibles are usually weak, the maxillæ are inclined over the labium, and the posterior legs have a comb of stiff curved spines beneath the tarsi. The web consists of a tangle of crossing lines, and the spider often constructs a tent-like retreat wherein the egg-sac is hung up.

20. Theridion lineatum (Clerck). Bristol (F. P. S.).

21. Theridion tepidariorum (C. L. Koch). Bristol (O. P. C.).

22. Pedanostethus lividus (Blackwall).

Leigh Woods (R. I. P.).

THOMISIDÆ

23. Xysticus cristatus (Clerck).

Leigh Woods (R. I. P.); Bristol (F. P. S.).

24. Philodromus aureolus (Clerck). Leigh Woods (R. I. P.); Bristol (F. P. S.).

DICTYNIDÆ

The species possess the calamistrum and cribellum and three tarsal claws, but the eyes, eight in number, are situated in two transverse rows, the laterals being in contact. They construct a tubular retreat with an outer sheet of webbing, which is covered with flocculent silk made with the calamistrum with threads from the cribellum.

25. Amaurobius ferox (Walckenaer). Leigh Woods (R. I. P.).

Known also under Ciniflo.

26. Amaurobius similis (Blackwall). Leigh Woods (R. I. P.).
Known also under Ciniflo.

27. Amaurobius fenestralis (Strœm). Leigh Woods (R. I. P.).

Known also as Ciniflo atrox.

OPILIONES

The harvestmen are spider-like creatures with eight long legs, the tarsi very long and flexible. Eyes simple, two in number, situated on each side of an eye eminence. Body not divided into two distinct regions by a narrow pedicle as in spiders; abdomen segmentate.

28. Phalangium opilio, Linn. Leigh Woods (R. I. P.).

29. Oligolophus agrestis, Meade. Leigh Woods (R. I. P.).

30. Nemastoma lugubre, O. F. Müller.

Leigh Woods (R. I. P.).

31. Liobunus rotundus, Latreille.

Leigh Woods (R. I. P.).

CRUSTACEANS

The amicable rivalry which in some points exists between the neighbouring counties of Somerset and Devon has never extended to the catalogues of their crustacean fauna. The contest would have been too unequal, so far at least as marine species are concerned. So much fresh water mingles with the salt in that part of the Bristol Channel which forms the northern boundary of Somerset, that only by a kind of courtesy can the county be said to have a sea-coast. It seems therefore to have retired altogether with a proud reserve from a competition in which it could not hope to take a leading place. Its natural history societies and serials leave the subject of carcinology on one side, as if scarcely worthy of a passing regard. No doubt in geology and archæology, in botany and architecture, there have been constantly been more obviously attractive objects of research. But there are some grounds for believing that even the modest branch of zoology here handled would well repay a patient student who could give time and trouble to its investigation. It would be unreasonable to expect a great harvest of rare crabs. Even the commoner Brachyura are not likely to be abundant. But, apart from these short-tailed decapods, the Malacostraca hitherto observed, few as they are, give assurance by their character and diversity that many companion species will eventually be found within the same territorial limits.

Among the Macrura, or long-tailed decapods, it is quite possible that the common lobster, Astacus gammarus (Linn.), may sometimes make its way up the Channel from Lundy Island, and it is highly probable that the river crayfish, Potamobius pallipes (Lereboullet), abundant in the Thames and Severn canal, may extend its range further westward. In regard to the latter species Mr. H. J. Charbonnier, of Bristol, in a letter dated August 21, 1901, says, 'I feel pretty sure that it occurs in Somerset.' He was unable however to make this statement more definite, so that it cannot be relied on for extending the distribution of the crayfish into this county. Leaving then the larger edible macrurans in the limbo of uncertainty, we must pass on to claim the occurrence of certain smaller but still useful and well esteemed forms, best known by the unscientific denomination of shrimps and prawns. Of these there are four species to be considered. They all belong to the same tribe, Caridea, which takes its name from karis, the Greek word for a shrimp. Little as they may at the first glance seem to resemble lobsters or crayfishes, they are essentially the same in structure. To impress this on the mind, nothing is needed but to take an opportunity of dismembering an example of a large species and another of a small one, so as carefully to compare the appendages of each in their orderly succession—eyes, antennæ, jaws and legs. The differences should be noted as well as the resemblances. When once such a comparison has been instituted with alert intelligence, a keener and kindlier regard is likely to be felt for every kind of crustacean, small or large, common or rare.

The massive front claws or chelipeds of the lobster and crayfish give them in our eyes an appearance very different from that of prawns and shrimps. But it should be borne in mind that in other regions there are shrimps as large as our crayfishes and prawns as large as our lobsters, and some of these great prawns have chelipeds longer than their bodies, so that in classification no exaggerated importance is attributed to size. A much more obscure feature separates all the Caridea with which we are here concerned from the larger British Macrura. In the latter the second and third pairs of legs are chelate, that is, the last two joints in these legs like the last two joints in the first pair form nippers, only they are nippers that are quite small instead of being massive. But in the Caridea the third pair of legs is always simple, its penultimate joint not being produced into a thumb to antagonize pincerwise with the finger-like terminal joint. By characters observed in the first two pairs of legs the Caridea are subdivided into four principal sections or legions. By what may for our purpose be described as a fortunate accident, the little flock of four species recorded in this county is distributed over three out of these four legions.

The first legion, Crangoninea, contains a single family, the Crangonidæ, which is here represented by the typical genus, Crangon, and the typical species of that genus, Crangon vulgaris, Fabricius, which may claim to be not only the common shrimp, but in most parts of England the commonest shrimp. By its extensive distribution, by its great abundance, by the facility with which it is captured on the shore and in shallow water, and by the appeal which it makes to the human palate this species holds a commanding position in popular notice and favour. Many, whom the logical definition of the class Crustacea would only bewilder, learn that the common shrimp is a crustacean with much satisfaction of mind. Its assignment to this county rests on rather slender but sufficient evidence. Adam White, in his List of the specimens of British animals in the Collection of the British Museum records it from 'Bridgwater: presented by W. Baker, Esq.' (fn. 1) This Mr. Baker of Bridgwater was a correspondent of Dr. Leach, and subsequently of Thomas Bell, both distinguished carcinologists, and one may be allowed to infer that the trusted correspondent of such men would neither have sent a lump of coal to Newcastle nor a common shrimp to the British Museum, unless such a specimen had been invested with the particular interest of coming from his own neighbourhood.

When crustaceans are being eaten little attention is paid to any thing but the muscular part and the well flavoured liver-like glands. These, like every other constituent of the complex organism, have their scientific interest, but they are not much studied except by a few specialists. The ordinary student of natural history employs himself chiefly just upon those portions to which the consumer is most indifferent, except in so far as he is disposed to consider them a tiresome incumbrance. For distinguishing the Crangoninea from the other legions some of these parts must be taken into account. In the first legs of Crangon one of these distinctive features will be found. They do not end in a proper claw, after the pattern or with the action of a pair of tongs. They are subchelate, that is to say, chelate only in a partial or modified condition. The penultimate joint or 'hand,' as it is sometimes called, is not produced parallel to the finger, but has a widened end across which the finger closes like the jointed lid shutting down upon the body of a lady's card-case. In the second pair of legs the antepenultimate joint or 'wrist' is undivided. These legs in the common shrimp end in a true chela, though a very small one, but as such a chela is not found in all the genera it cannot be used as a character of the legion. It should not be thought that the whole interest of the subject is exhausted even when every cell and fibre, every limb and segment and gill of the adult animal has been examined. The evolution from the egg through several successive exuviations or moultings of the integument exhibits many surprising changes. The young one is far from having, to start with, the long array of appendages for which the fully grown find employment. Its eyes are for some time fixed instead of movable. The telson is triangular both first and last, but a curious thing is that the youthful telson broadens from a narrow base, then becomes quadrangular, and finishes up by being narrowest at the tip, where at first it was most broadly expanded. (fn. 2) Nature may be trusted not to make these changes out of mere caprice. In correlation with others, they express the endeavour to give the animal in the different stages of its existence the most favourable opportunities for feeding, migrating, and escaping dangers.

The second legion is called Polycarpinea or many-wristed, and the meaning of this peculiar name will help to explain one of the marks used as a characteristic of the preceding legion. It was there observed that the second legs had an undivided 'wrist.' The manner of the speech that attributes a wrist to a leg is rather unconventional. The awkwardness of it is partly disguised if, instead of saying 'wrist,' we use the classical equivalent 'carpus' to designate the fifth or antepenultimate joint of the malacostracan trunk-limb. Normally these appendages are sevenjointed, but the simplicity of the counting is sometimes spoiled by coalescence, two joints running into one, and sometimes it is spoiled in the opposite direction by a joint being broken up into jointlets, as when a single bar of iron is converted into a chain of several links. This is what happens to the fifth joint in the second legs of the Polycarpinea. That legion comprises four families, the one with which we are here concerned being called the Pandalidæ from the premier genus Pandalus, Leach. The species Pandalus montagui, Leach, is a large, well known, and tolerably abundant English prawn, though not the commonest and most familiar kind to which that vernacular name is given. On parts of our east coast however it would seem to be the predominant form. But it occurs in several localities, and among these, according to Adam White, 'the Rev. Alfred Norman has found it at Clevedon in Somerset.' (fn. 3) It was till lately regarded as a character of the family that the front legs should be simple, but a French author, M. Maurice Caullery, found that this did not apply to a species which he examined from the Bay of Biscay. He suggested therefore that in regard to other forms observers might have overlooked the pincers owing to their extreme minuteness. On this point Mr. (now Dr.) W. T. Calman writes as follows: 'So far as concerns the British species, at any rate, I am able to confirm this suggestion of Mr. Caullery. A microscopic but perfectly formed chela is found on the first peræopods of all of them, including the familiar type of the genus, P. montagui . . ., which for more than three quarters of a century has been described as having the first legs "simple." Even under the microscope the chelate termination may easily escape notice, on account of the brush of setæ among which it is partly hidden. Closer examination however reveals the minute dactylus, separated from the propodus by a distinct articulation and, as it is easy to convince oneself by touching with a needle, freely movable. I am unable to say whether muscles for opening and shutting the chela are present. Both the fingers are slightly curved and a tuft of long curved setæ springs from the inner margin of each. The fingers are from one-twelfth to one-tenth of the whole length of the propodus in adult specimens of P. montagui, and proportionately a little longer in young individuals. No differences worthy of note are observable in the other British species.' (fn. 4) It may be further observed that in this genus the upper edge of the beak or rostrum is armed with teeth or spinules that are not rigid but movable, and that the second legs are not strictly a pair, one being considerably longer than the other. Among the British species, Pandalus montagui is distinguished by having the wrist in the shorter of these legs, which is on the right side, subdivided or annulated much more copiously than it is in the companion species. (fn. 5)

The third legion, the Monocarpinea, with undivided wrist in the second pair of trunk-limbs, could not by that feature alone be distinguished from the first legion. But whereas among the Crangoninea the second legs are feeble and generally short, in the numerous families of the third legion they are as a rule long or strong, and if these marks happen to fail the first legs come to the rescue by being either simple or chelate, not subchelate as in the 'shrimps.' Two of the families are represented in this county, each so far as at present reported only by a single species. The Palæmonidæ, which are extensively distributed in the rivers as well as the seas of the globe, include Leander serratus (Pennant), the common prawn of British markets, together with other less common species of the same genus, and besides these a sort of amphibious species, Palœmonetes varians (Leach). The last is the only one as yet on record for Somerset. It is amphibious, not in the sense of being able to inhabit both land and water, but as being what is now called 'euryhaline,' latitudinarian as to salt, retentive of life in fresh water but not incapable of existence in brackish water or the sea. Accordingly Adam White, after mentioning various marine localities for this species, adds, 'the Rev. Alfred Norman finds it off the coast of Guernsey, and in a note he kindly informs me, "I have taken this species in great abundance at Clevedon, in a ditch far above ordinary high-water mark, of which the water was scarcely at all brackish; it was in company with myriads of Rissoa ventricosa. I found some also further up in a stream of clear running water, along with Aplexus hypnorum and other freshwater shells." ' (fn. 6) From this and other samples of careful observation it is easy to augur that, had Canon Norman, F.R.S., the distinguished naturalist referred to by White, spent much instead of little time in this county its crustacean records would have been wonderfully amplified.

The macruran species still remaining to be noticed belongs to the family Pasiphæidæ, of which the leading genus is Pasiphœa, Savigny. The species was first introduced as British by Adam White, Leach having left it unpublished, though with a manuscript name, P.savigniana, attached to specimens in the British Museum. Under the name P. savignyi Milne-Edwards in 1837 published a description of these specimens, but regarded their place of origin as 'Patrie inconnue.' (fn. 7) White, adopting the name P. savignyi given by Milne-Edwards, which he translates into 'Savigny's shrimp,' explains that the specimens came in part from Bridgwater, presented by W. Baker, Esq., and in part from Ireland, presented by the Rev. J. Bulwer. (fn. 8) Bell soon after identified the species with the earlier Pasiphæa sivado, Risso, and White in 1857 accepted this name, which he does into English as the 'sword shrimp.' Part of his account of it is well worth quoting. ' This shrimp,' he says, 'is very much compressed, and the body, when alive, is white and transparent, each joint being banded with red; the eyes are black; the antennæ and legs are red, and the tail-plates are dotted with red. I am indebted to the Rev. Alfred M. Norman for the following note: "This beautiful crustacean occurs in the British Channel at Clevedon, occasionally in great abundance. It was called by the fishermen who procured them for me 'the White Shrimp.' It is taken in nets suspended from poles and placed near the mouth of the little stream that runs into the Channel at 'the Pill'; these nets are set to take shrimps, sprats and other fish which the tide as it goes out leaves in them. Although the fisherman is always on the spot to secure his fish as the tide recedes, he assures me he has never once seen a Pasiphœa alive. I conclude therefore that they cannot bear exposure to the air, and die instantly on leaving the water. Colour white, and the appearance jelly-like; the antennæ, articulations of the abdomen, pedipalps, hands and caudal laminæ are more or less coloured with rich crimson, as Risso has described Mediterranean examples. It is a most lovely and remarkable species." ' (fn. 9) This then may be regarded as the chief glory of the crustacean fauna belonging to this county. In appearance it has more the character of a prawn than a shrimp, though the insignificance of its rostrum at once discriminates it from the Palæmonetes before mentioned. The conspicuous longfingered pincers of the first and second pairs of legs are also highly distinctive. In these limbs the slender thumb and finger are beautifully armed on the inner margin, each with a long comb of glass-like teeth, formed by articulated spines varying from forty to eighty in the several rows, the smallest number occurring on the thumb or immovable finger of the first pair and the highest on the movable finger of the second.

Of sessile-eyed Malacostraca the county records are still more scanty than those of the stalk-eyed division. This can be attributed with the utmost assurance not to dearth of species but to want of any long resident observers who thought it worth while to record them. Of the Isopoda the family Sphæromidæ yields a single species, Sphœroma hookeri, Leach, concerning which White remarks with a sort of customary formula that 'the Rev. Alfred Norman finds it at Clevedon and in Guernsey.' (fn. 10) The name of the family as of the genus refers to a particular habit and capacity in the animals comprised therein of assuming a spherical form. This is familiar to every one in a family of terrestrial isopods which will presently demand attention. In both families the adaptive structure is similar. That the Isopoda, including our common woodlice, are Malacostracan crustacea is by no means universally understood. The learned Savigny, whose name has been noticed above in connection with the genus Pasipbœa, demonstrated in 1816 the parity of organization between the stalk-eyed and sessile-eyed crustaceans. He made it clear that, though in general the former group have ten legs and the latter have fourteen, the difference depends only on the fact that the Decapoda have converted the first two pairs of legs into jaws or mouthorgans. The Tetradecapoda, retaining their seven pairs of appendages in more or less leg-like form, have also kept as a rule seven segments of the middle body freely movable one upon the other. This is managed by their having between one segment and another a transverse strip of integument not highly chitinized or solidified by carbonate of lime but thinly and flexibly membranaceous. Thus the segments can slide over one another to a certain degree when the body is extended, and on the other hand can usually be so far stretched apart as to enable the animal with the front of its forehead to touch the extremity of its tail. In some cases this only amounts to a process of doubling up, but in many of the Sphæromidæ, while the middle segments are dorsally distended, their lateral plates fold one over the other so that a compact little ball is produced, within which are sheltered the lashes of the antennæ, the mouth-organs, the more or less uniform legs and the delicate branchiæ of the pleon or tail. Whether Sphœroma hookeri, with two faintly marked longitudinal carinæ on the upper surface of its terminal segment, can thereby be effectively distinguished from the earlier Sphæroma rugicauda, Leach, is perhaps still open to question.

Of the land Isopoda or woodlice, in the family Armadillidiidæ, I can report Armadillidium nasatum, Budde-Lund, from Leigh Woods near Clifton. The members of this family are sometimes irreverently called 'pill-bugs,' in allusion no doubt as well to their shape when rolled up as to their actual use in ancient medicine. In these globe-forming animals the breadth is commonly about half the length. The species A. nasatum, meaning the Armadillidium with a nose, has evidently received its specific name in reference to the part called the epistome, by which it is pretty easily distinguished from Armadillidium vulgare. In the latter the epistome scarcely rises above the frontal line, but in A. nasatum it forms a subquadrangular plate much surpassing the frontal margin. (fn. 11) It is scarcely necessary to insist that at least several of the terrestrial isopods known to frequent the adjoining counties certainly also occupy the woods and gardens, the highways and byways, the underside of flat stones, the inside of ants' nests, and other their favourite retreats, as freely in Somerset as elsewhere.

In the companion group of the Amphipoda just one species may be said to save the situation. Of Dexamine spinosa (Montagu) the often quoted Adam White says once again that 'the Rev. A. Norman has found it at Clevedon, Somerset.' (fn. 12) When freshly captured this is among the brightest and most gaily coloured of its order. It may be regarded as in itself a guarantee that where it is found there also will occur many other species of Amphipoda of similar habits. Sand and sea-weed, various floating objects, muddy ooze and submerged timber supply them with food and shelter, so that within tide-marks, and in shallow water or in deep, all round our coasts many kinds are to be found, and some of them in great abundance. Without here entering into the minutiæ of their structure, it may suffice to say that the Amphipoda are completely distinguished from the other sessile-eyed group, the Isopoda, by the position of the breathing organs. The latter have their branchiæ, except in one aberrant section, situated in the caudal part or pleon. In the Amphipoda the respiratory sacs or vesicles, which are often simple, but sometimes pleated, twisted, or otherwise diversified, are always attached to limbs of the peræon or middle body.

That Entomostraca are well represented in this county is chiefly a matter of inference. It would be what logicians call a petitio principii to say that they are well represented in all counties, and therefore in this, but it would be a tolerably safe inductive conclusion. Of the Phyllopoda the shield-bearing Apus cancriformis, Schæffer, is recorded from Bristol and from Devonshire, and the elegant Chirocephalus diaphanus, Prevost, which unhampered by valves or carapace keeps up the rhythmical movement of its leaf-like limbs, is recorded in like manner both from Devonshire and the neighbourhood of Bristol. The old schoolmen are said to have propounded the subtle question whether angels in passing from place to place pass through the intermediate space. We may ask whether it is at all likely that the many-footed Apus or the translucent fairy shrimp could have possibly passed from Bristol into Devon without colonizing Somerset on their road. We know at any rate that in past ages the county was not destitute of phyllopods, since Estheria minuta var. brodieana is reported by Professor Rupert Jones from Somerset as occurring in the Rhætic formation, which consists of passage beds between the Lias and Trias. (fn. 13)

If the Phyllopods and the ubiquitous Cladocera have here to be taken on trust, for the third section of the Branchiopoda there is direct evidence. This section, the Branchiura, is a small one, and does not very clearly conform to the characters of the other branchiopods. It includes the single parasitic family of the Argulidæ, in which the species Argulus foliaceus (Linn.) has long been known in England and elsewhere as a parasite upon various freshwater fishes and tadpoles. Mr. H. J. Charbonnier, already mentioned, has informed me by letter that he once took it at Keynsham in one of the streams, and studied its behaviour in his aquarium with great delight. He attributed to it the death of some sticklebacks. From the scene of slaughter, in which the Argulus was observed swimming free, according to its wont after a satisfying meal, Mr. Charbonnier removed it to another aquarium where he had some other sticklebacks. Here, the letter continues, 'he was immediately seized and vigorously "chewed," but presently he slipped through the "gill" of his captor and creeping over his head proceeded to insert his rostrum just over the fish's brain.' In Argulus the second maxillæ are transformed into sucking discs by which the bloodthirsty little creature adheres to its involuntary host. A Japanese species has recently been made known in Europe, very far exceeding in size those found in European waters. The Japanese fishes would perhaps be content with the smaller pattern.

Of the Ostracoda species in Great Britain are very numerous. Some of these are rare, but several are so impartially distributed north and south, east and west, that they may reasonably be expected to occur in every county. They do not however tempt many observers to examine them. Not only are their bodies and limbs almost always very minute, but they are rather obstinately withdrawn from view by the owners whenever outside curiosity becomes in the least obtrusive. The desired privacy is secured by the pair of sheltering valves which make an ostracode look more like a tiny mollusc than a crustacean. Even after death the closure of the valves is very persistent, though not invincible in the hands of an expert. The only species actually recorded for Somerset seems to be Cytheridea torosa (Rupert Jones), which Dr. G. S. Brady reports from Weston-super-Mare on the authority of the Rev. A. M. Norman. (fn. 14) It belongs to the Podocopa, a tribe of the Ostracoda which manages to support existence without a heart. Within this tribe it is a member of the family Cytheridae, which generally have hard calcareous valves, uneven of surface, bare or sparingly hirsute, and united by a toothed hinge. The animals are incapable of swimming. The genus Cytheridea, Bosquet, was originally founded on forms from tertiary strata of France and Belgium. The species C. torosa is according to Dr. Brady rather exceptional in the genus, for while classing it as a true Cytheridea, he qualifies his opinion by adding that 'there remains one important character in which, so far as I know, this species stands alone among the Ostracoda, namely, the enormous number of ova borne at a single time by the female; how far this may prove to be of generic importance future investigations must show; it is at any rate an interesting fact, and one which fully accounts for the immense numbers in which the species is often found.' (fn. 15)

Of the Thyrostraca, that is, cirripedes or barnacles, apparently no definite record awards any to the Somerset coast. Yet many species must certainly reach its waters in attachment to the hulls of vessels and other floating objects. Of the sessile forms included in the family Balanidæ, at least the wide-ranging Balanus improvisus, Darwin, may be expected to rank as a resident on these shores. There can scarcely be anything in the conditions of the estuary to banish it from this part of the Bristol Channel, for this is 'a Balanus capable of living in freshwater and likewise in the saltest seas,' whereas 'even brackish water is a deadly poison to several, probably to most, species of the genus.' (fn. 16)

That even B. improvisus can live without an occasional savour of salt in its diet is not perhaps to be maintained, but since it can exist at Woolwich on the Thames, it may very well do the same at Weston on the Severn or on the Sea.

Footnotes

1 Crustacea, p. 37 (1850)
2 See Sars, Bidrag til Kundskaben om Decapodernes Forvandlinger, pt. 3 (1890), and H. C. Williamson, 'On the larval stages of Decapod Crustacea—the Shrimp (Crangon vulgaris, Fabr.),' Fishery Board for Scotland Report, pt. 3 (1901).
3 Popular History of British Crustacea, p. 126 (1857).
4 Annals and Magazine of Natural History, ser. 7. iii. 28 (1899). The dotted space in the quotation marks only an omitted reference to an illustrative figure. The word 'propodus' is equivalent to 'hand' or penultimate joint.
5 Loc. cit. p.39.
6 Popular History of British Crustacea, p. 135 (1857).
7 Histoire Naturelle des Crustacés, ii. 426.
8 List of the specimens of Crustacea in the British Museum, p. 80 (1847); and List British Animals in British Museum, pt. iv.; Crustacea, p. 43 (1850).
9 Popular History of British Crustacea, p. 137. It may be remarked that the 'pedipalps' are now more commonly spoken of as the third maxillipeds, the articulations of the abdomen as segments of the pleon, and that the caudal laminæ include the telson and the uropods, the latter being the appendages of the sixth pleon-segment.
10 Loc. cit. p. 245.
11 Budde-Lund, Isopoda Terrestria, p. 51 (1885).
12 Popular History of British Crustacea, p. 178.
13 Fossil Estheriæ, Palæontographical Society, p. 67 (1862).
14 Transactions of the Linnœan Society, vol. xxvi. pt. 2, p. 426 (1868).
15 Loc. cit.
16 Darwin, Monograph of Balanidæ, Ray Society, p. 253 (1854).