Phyllidiacea.] 



MOLLUSCA. 



65 



Shell ovate, subpellucid, provided with from ten to twelve 

 moniliform, tesselated, red rays ; apex acute, and submarginal ; 

 ground colour of the exterior of an opaque reddish-white. 

 Length somewhat more than a quarter of an inch ; breadth 

 about a fourth narrower than its length. 



This shell was discovered by Professor Forbes, on the Manx 

 coast, adhering to shells in deep water, who says it is allied to 

 the Patella virginea, but differs from that species, in never at- 

 taining so large a size ; and in the markings, especially in the 

 young shell, being of a bluish-white colour, with red rays. 



Genus 18 Chiton.— Linnaeus. 



Shell elongated, or oblong-oval ; consisting of eight valves, 

 placed transversely on the back of the animal, which is convex; 

 these valves are moveable and imbricated, the edge of the one 

 resting on that below it, the terminal ones being rounded exte- 

 riorly; valves surrounded by a coriaceous marginal skin, or 

 ligament ; several of the valves are provided with marginal 

 teeth, which are, however, concealed by the marginal liga- 

 ment. 



Section I. — Marginal ligament spinous. 



1. Chiton fascicularis, pi. XXI, f. 5 and 8. 



Chiton fascicularis, First Ed., pi. 35, f. 5 and 8; Linne, p. 

 1106; Montagu, p. 5, pi. 27, f. 5; Maton and Rackett, p. 21, 

 pi. 1, f. 1 ; Brown, Ency. Brit., p. 402 ; lb., Wernerian Mem., 

 p. 503; Fleming, p. 288 ; lb., Edin.Ency., VII, p. 103; La- 

 marck, Syst., VI, pt. 1st, p. 321 ; Lowe, Zool. Journ., II, p. 96; 

 Ency. Meth., pi. 162, f. 15 ; Forbes, p. 37- 



Shell subcarinated ; the carina of the valves longitudinally 

 striated, their sides thickly studded with coarse, elevated gra- 

 nules, which are distinct to the naked eye ; the centre of the 

 first and last valves destitute of the longitudinal striae; ligamen- 

 tary margin also provided with coarse granulations, more or less 

 spinous, and furnished with fasciculi of grayish, short bristles, 

 situate at the interstices of the valves, on the sides, and round 

 the first and terminal valves ; marginal teeth of the valves vari- 

 able, sometimes having three notches on each side, with the 

 intermediate space crenulated; these crenulations are sometimes 

 so deep in the last valve, and reach within a short distance of 

 either extremity, that they may almost be considered as teeth ; 

 the colour is variable, generally cinereous, or dark olive-green ; 

 marginal fringe very distinct, and bristly. Length varying from 

 a quarter to three-quarters of an inch ; breadth somewhat more 

 than half its length. 



This species seems liable to variety, as it will be noticed that 

 fig. 8, which was drawn from one procured by Dr. Goodall on 

 the rocks at Weymouth, has twenty-one tufts of hairs, one of 

 which is placed on the extreme point of the terminal valve, 

 while, in general, only twenty fasciculi are met with, none being 

 on the terminal valve. Montagu says that this species has only 

 eighteen tufts. 



This shell is not uncommon on many of the British coasts ; 

 and is a deep water species, generally found attached to oysters 

 and stones. The very fine specimen from which fig. 5 was 

 drawn, was procured at Lough Strangford, County of Down, 

 Ireland, where it is plentiful of that size. The smaller one, fig. 

 8, is not uncommon in the Frith of Forth. 



2. Chiton discrepans, pi. XXI, f. 20. 



Chiton discrepans, First Ed., pi. 35, f. 20 ; Chiton f 



Ency. Meth., p. 163, f. 1 1, 12 ? 



Shell much elongated, narrow, acutely carinated ; valves 

 shield-shaped, and acutely pointed beneath ; along the centre 

 of the valves is a lance-shaped elevation, which is striated lon- 

 gitudinally ; valves covered with strong, round, elevated, regu- 

 larly set papilla?, except at the edges, which are plain ; at the 

 junction of each valve is a tuft of strong, straight, stiff bristles ; 

 whole margin beset with rather distant, very minute, gray hairs; 

 valves generally of an orange-yellow ; margin deep umber- 

 brown. 



This species differs from the preceding in being much more 

 carinated, in the valves being a third narrower, in the fasciculi 

 of bristles being shorter and more stunted, in the papillae being 

 round instead of oval, and the whole shell being much narrower 

 in proportion to its length. 



Several specimens of this shell, new to the British Concho- 

 logist, were sent to me from George Lyons, Esq., of Tenby, 

 Wales, where it is common, and where it was mistaken for the 

 C. fascicularis. 



3. Chiton crinitus, pi. XXI, f. 20. 



Chiton crinitus, First Ed., pi. 35, f. 20; Pennant, IV, p. 71, 

 pi. 36, f. 1, 1 ; Gmelin, Linn. Syst., p. 3206; Montagu, p. 4 ; 

 Maton and Rackett, p. 20; Fleming, Edin. Ency., p. 103. 



" Shell with seven valves ; thick set with short hairs ; five- 

 eighths of an inch long. Inhabits the sea, near Aberdeen." — 

 Pennant. Mr. Boys informed Montagu that he had also found 

 it at Sandwich. 



Section 11. — Marginal ligament striated, or papillose. 



4. Chiton l*vis, pi. XXI, f. 10, 11. 



Chiton IcEvis, First Ed., pi. 35, f. 10, 1 1 ; Pennant, IV, p. 72, 

 pi. 36, f. 3 ; Montagu, p. 2 ; Brown, Ency. Brit., p. 402 ; lb., 

 Wernerian Mem., p. 503; Fleming, Edin. Ency., p. 102 ; lb., 

 Brit. An., p. 90 ; Forbes, p. 37 ; Maton and Rackett, p. 21. 



Shell with eight smooth, slightly carinated, pointed valves, 

 generally of a deep reddish-brown, mottled with white, but is 

 liable to considerable variety both in colour and markings, with 

 remote, nearly obsolete stria;; margin broad, fringe very minute, 

 with fine decussated stria;. Length a little more than half an 

 inch; breadth more than half its length. 



Found on many of the coasts of Great Britain and Ireland, 

 in deep water, although it may be considered a local species. 

 First noticed in Loch Broom, Rossshire ; the Frith of Forth, 

 coast of Northumberland, Devonshire, Manx coast, and at 

 Rathgarmont, Lough Strangford, Ireland. 



5. Chiton achatinus, pi. XXI, f. 4, 12, 13, and 15. 

 Chiton achatinus, First Ed., pi. 35, f. 4, 12, 13, and 15; 



Brown, Ency. Brit., VI, p. 402. 



Shell very oblong; valves narrow, and long in proportion to 

 their breadth, considerably elevated in the centre, but not cari- 

 nated ; pale lilac-coloured in some specimens, and olive-green 

 in others, beautifully marbled with reddish-brown, and indis- 

 tinctly striated transversely, following the wave of the valves ; 

 both anterior and posterior terminal valves are covered with 

 transversely arcuated stria;, and the whole of them very minutely 

 shagreened ; margin with upright oval, minute specks of sha- 

 green. 



