CONCHACEA.] 
MOLLUSCA. 
93 
two lateral, remote, muscular impressions; pallial impression 
entire ; ligament external, inserted into a deep marginal, poste- 
rior, dorsal sinus. 
1 . Cyprina vulgaris, pi. XXXVII, f. 1 , and pi. XXXVIII, 
f. 11. 
Cyprina Islandica, First Ed., pi. 18, f. 1, and pi. 19, f- 11 ; 
Lamarck, V, p. 557 > Fleming, p. 443 ; Forbes, p. 47 ; Venus 
Islandica, Donovan, III, pi. 77 ; Montagu, p. 114; Turton, 
Biv., p. 135; Venus mercinaria, Pennant, IV, p. 94, pi. 53, 
f. 47. 
Shell strong, thick, convex, suborbicular ; umbones large, 
pointed, approximate, placed near the anterior side, and much 
inflected, destitute of a lunule beneath them ; outer surface 
with numerous, rather close-set, concentric, somewhat irregular 
striae, and covered by a strong, horny, blackish-brown, glossy 
epidermis, which assumes a wrinkled, sublamellated character 
towards the base of the valves ; inside smooth, white, but not 
glossy ; pallial impression destitute of a sinus ; margin plain, 
and acute. 
It has been found upon comparison, that this shell is not 
identical with C. Islandica. 
This species is not uncommon in deep water, on most of 
the British and Irish coasts. The ordinary size of the shell 
is that on pi. XXXVII, f. 1 ; and the gigantic specimen from 
which I took f. 11, pi. XXXVIII, was dredged in the Irish 
Channel, and is in the cabinet of William Nicol, Esq., of 
Edinburgh. 
In the young condition, this shell is covered with a shining, 
pale yellowish chestnut-coloured epidermis. 
Genus 14 — Las^ea Leach. 
Shell equivalve, inequilateral, somewhat inflated ; hinge not 
quite central ; with approximate, small cardinal, and a remote, 
lateral, conspicuous tooth in one valve, and a concave, remote, 
strong, lateral tooth in the other ; margin plain ; ligament in- 
ternal. 
1. Las^a rubra, pi. XXXVI, f. 17, 18. 
Laseea rubra, First Ed., pi. 20, f. 17, 18; Leach, MSS., p. 
7 ; Brown, Conch. Text Book, p. 128, pi. 16, f. 16; Cardium 
rubrum, Montagu, p. 83, pi. 27, f. 4 ; Maton and Rackett, p. 
66 ; Kellia rubra, Turton, Biv., p. 57 ; Fleming, p. 430 ; 
Forbes, p. 49. 
Shell convex, inequilateral, somewhat broader than long, 
smooth, glossy, pellucid, of a purple-red colour; umbones 
produced, very slightly inflected ; hinge with nearly obsolete, 
cardinal teeth, the lateral ones distinct; inside glossy, red; mar- 
gin plain. Diameter not an eighth of an inch. 
Inhabits the crevices of rocks on most of the British and 
Irish coasts. 
Sub-Division — Fluviatile. 
Shells covered with a spurious epidermis, and the hinge pro- 
vided with lateral teeth. 
Genus 15. — Cyclas. — Lamarck. 
Shell thin, equivalve, subequilateral, ventricose, transverse, 
or semiorbicular ; closed all round ; beaks mostly tumid ; car- 
dinal teeth very small, sometimes hardly perceptible ; with one 
plicated or lobed tooth in the left valve, and two divergent in 
the other ; lateral teeth transversely elongated, acute, com- 
pressed, or lamelliform, double in the left valve ; clothed with 
a thin, horny epidermis ; two lateral, ovate, muscular impres- 
sions ; pallial impression entire, destitute of a sinus ; ligament 
external. 
1. Cyclas rivicola, pi. XXXIX, f. 16, 17, 18. 
Cyclas rivicola. First Ed., pi. 17, f. 12 ; Lamarck, V, p. 558 ; 
Cyclas cornea, Pfeiffer, Land un Was. Sc., p. 121, pi. 5, f. 3, 
4, 5; Turton, Brit. Biv., p. 248, pi. 11, f. 13; Ib., Man., p. 12, 
f. 1 ; Fleming, Brit. An., p. 453 ; Alder, Mag. Zool. and Bot., 
II, p. 118; Cyclas cornea, Drapernaud, Hist, des Moll., p. 128, 
pi. 12, f. 1, 2, 3; Tellina cornea. Wood, pi. 46, f. 3; Cardium 
corneum, Montagu, p. 86. 
Shell thin, pellucid, convex, ovate; covered by a horny- 
green epidermis, frequently marked with paler transverse 
zones ; furnished with strong, close, regular, concentric striae ; 
umbones obtuse, central, and slightly turned to one side ; 
hinge with a very small cardinal tooth in the left valve, which 
fits into the space between two small, but rather produced 
teeth in the opposite valve ; both valves provided with pro- 
minent, lateral, laminated teeth on each side, those of the 
right valve hardly rising above the margins, but in the left 
valve projecting considerably beyond them ; inside smooth, 
bluish-white, dull in the concave disk, but glossy towards the 
margin ; an indistinct, pretty large, muscular impression near 
the anterior margins, and a narrower, obscure one in the pos- 
terior sides. 
This is the largest species of the genus, sometimes mea- 
suring five-eighths of an inch in length, and seven-eighths in 
breadth. 
Found plentifully in the Thames at Battersea, and also near 
Red House, and in the neighbourliood of Oxford ; of a large 
size in the Trent, near Burton ; and in many slow rivers in 
England. 
2. Cyclas cornea, pi. XXXIX, f. 19. 
Cyclas cornea. First Ed., pi. 17, f. 15; Pfeiffer, p. 120, pi. 5, 
f. 1, 2; Turton, Brit. Biv., p. 248, pi. 11, f. 14; Ib., Man., p. 
13, f. 2; Fleming, Brit. An., p. 452 ; Forbes, p. 49 ; Thomp- 
son, Ann. and Mag. Nat. Hist., VI, p. 52 ; Alder, Mag. Zool. 
and Bot., H, p. 118; Cyclas rivalis, Drapernaud, Hist, des 
Moll., H, p. 202, No. 387 ; Tellina cornea, Gmelin’s Xinne, I, 
p. 1120, No. 72. 
Shell subglohular, ventricose, thin, semitransparent ; with 
concentric, nearly obsolete striae ; umbones obtuse ; epidermis 
greenish horn-colour, with darker zones, and bordered with a 
broad, yellowish hand ; inside dull bluish-white. Length three 
and a half eighths of an inch ; breadth half an inch. 
A very distinct variety, considerably less than the ordinary 
size, with the teeth larger in proportion, and of a lemon-yellow 
colour, was found by Mr. Glover, in the Leven, not far from 
Ambleside. 
