lOi 
MOLLUSCA. 
only wanting, but where, as in tlie Lucinae, tlie impression of the 
anterior muscle is very long * * * § ; 
3. Tlie thick species with radiated ribs, in which the fold is also 
wanting, and which connect the genus Venus with that of the 
Venericardiaf. In the 
Capsa, Brufj. 
Already separated from the former, there are two teeth on the 
hinge on one side, and a single, but bifid one, on the other ; the 
lunula is wanting, the shell convex, and the fold, indicative of the 
retractor of the foot, considerable;];. 
Petricola, Lam. 
Also separated from the same genus ; the Petricolae, on each side, 
have two or three very distinct teeth on the hinge, one of which is 
forked. The shell is more or less cordiform, but as they inhabit 
the interior of stones, it sometimes becomes every irregular. Judg- 
ing from the marginal impressions of their mantle, their tubes must 
be very large §. 
CoRBULA, Brug. 
Similar in form to the triangular Cytherea', or cordate ; but a single 
stout tooth in the middle of each valve, corresponding to the side of 
its antagonist. The lagiment is internal; the tubes must be short, 
and the valves but rarely equal ||. 
The fossil species are much more numerous than the living 
ones^. 
Some of them live in the interior of stones**. 
Mactra, Lin. 
The Mactrm are distinguished from the other Testacea of this family 
bv their ligament being internal, and lodged throughout in a trian- 
gular depression, as in the oysters ; they all have a compressed foot 
fitted for crawling. In the 
MxACTra, Lam., 
Or the Mactrae properly so called, the ligament is accompanied 
to the left valve, before and behind, by a pi’ojecting jjlate which is 
received between two others on the right one. Close to the ligament, 
* J'en. tigrina, Chemn., VII, 37, -90 ; — J'en. punctata, Ib. 397. 
p J'en. pectinata, Chemn., VII, 39, 419 — the genus Arthemis, Oken. 
Ven. deflorata, Chemn., IV, ix, 79 — 82. 
§ Ven. lajncida, Chemn., X, 172, 1664, and the Rufellaria of M. Fleriau de 
Bellevue; — Fen. perforans. Montag., Test. Brit. pi. iii, f. 6 ; — Donax inis? 
Chemn., VII ; xxvi, 270. 
II See Encyc. Method., Vers, pi. 230, f. 1, 4, 5, 6. 
^ Corfmla gatlica ; — G. complanata ; — G. omhonella, Desh., Coq. Foss., des Env. 
de Paris, t. I, pi. 7, 8, 9. 
** T'chus woiisO’osc, Chemn., VII, 42, 445 — 446. 
