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, 

 t. 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 Lasjea 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. Lasjea rubra, pi. XXXVI, f. 17, 18. 



Lascea 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; lb., 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 neighbourhood 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; Pfeifler, p. 120, pi. 5, 

 f. 1, 2; Turton, Brit. Biv., p. 248, pi. 11, f. 14; lb., 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., II, p. 118; Cyclas rivalis, Drapernaud, Hist, des 

 Moll., II, p. 202, No. 387 ; Tellina cornea, Gmelin's Linne, I, 

 p. 1120, No. 72. 



Shell subglobular, ventricose, thin, semitransparent ; with 

 concentric, nearly obsolete stria? ; umbones obtuse ; epidermis 

 greenish horn-colour, with darker zones, and bordered with a 

 broad, yellowish band ; 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. 



2 A 



