13 
CONCHiE MARINE. 
Mostly no lateral teeth; the whole, shell frequently covered with an epidermis , except at 
the beaks. 
Cyprina. — Shell equivalve, inequilateral, obliquely cordate ; the beaks obliquely curved; 
three unequal cardinal teeth, approximating at their base, and diverging a little 
above: a lateral tooth distant from the hinge, placed on the anterior side, some- 
times obsolete. The callosities of the nymphse large, arched, terminated near the 
beaks by a pit. Ligament external, sunk in part under the beaks. 
Plate VII. Fig. 2. (a) C. Islandica. (Venus Islandica. — Linn.) 
( b ) Hinge of ditto. 
Cytherea. — Shell equivalve, inequilateral, suborbicular, triangular, or transverse : four 
cardinal teeth in the right valve, three of which diverge and approximate at their 
base, and one quite insulated, situated under the lunula: three diverging cardinal 
teeth in the other valve, and a pit rather distant, parallel to the margin. No 
lateral teeth. 
I. Internal margin of the valves very entire. 
(а) Anterior cardinal tooth having a striated canal or dentated border. 
Plate VII. Fig. 3. (a) C. tripla. (Venus tripla. — Chem ) 
( b ) Hinge of ditto. 
(б) Anterior cardinal tooth without the striated canal or dentated border. 
Plate VII. Fig. 4 C. picta. (Venus picta.— Chem.) 
II Internal margin of the valves crenated or dentated. 
Plate VII. Fig 5*. C. meroe. (Venus ineroe. — Linn.) 
Venus. — Shell equivalve, inequilateral, transverse or suborbicular : three approximate 
cardinal teeth in each valve, the lateral ones diverging at the summit. Ligament 
external, covering the scutcheon. 
1. Internal margin of the valves crenated or dentated. 
(а) Shells with lamellar strive. 
Plate VII. Fig. 6. (a) V. verrucosa. (Idem. — Linn.) 
( h ) Hinge of ditto. 
(б) Shells without lamellar strive. 
Plate VII. Fig 7- V. flexuosa. (Idem.— Gmel.) + 
II The internal margin of the valves very entire. 
Plate VII. Fig. 8. V. papilionacea. (V. rotundata. — Gmel ) 
* This species is the Donax meroe of Lamarck; but, as it agrees in the hinge, and in other particulars, 
with the Cytherea genus, I have removed it to its present situation, where it forms, with a few others of a si- 
milar character, a very interesting group, which are distinguished by the remarkable cavity in which the li- 
gament is situated, in addition to the crenated margin. 
f Lamarck has named this species Cytherea flexuosa, but its hinge is decidedly that of a Venus. 
