ACKPHALA TESTACEA. 
103 
these same summits there is almost always an oval impression termed 
the anus or lunula * * * § . 
The animal is always furnished with two more or less protractile 
tubes, sometimes united, and with a compressed foot, which enable it 
to crawl. 
M. Lamarck appropriates the name of V enus to those which have 
three small diverging' teeth under the summit. This character is 
particularly well marked in the oblong and slightly convex spe- 
cies f . 
Some of them — the Astart^, Sowerb., or Grassing, Lam., — have 
only two diverging teeth on the hinge, and approach the Crassatellae 
in their thickness and some other characters J. 
Among the cordiform species, that is, those which are shorter and 
have more convex nates, and with more closely approximated teeth, 
we should remark those where the plates or transverse striae terminate 
in crests § or tuberosities ||, and those that have longitudinal ribs and 
crests elevated behind. 
We subseqiiently and gradually come to the Cythere^e, Lam., 
which have a fourth tooth on the right valve, projecting under the 
lanula, and received into a corresponding cavity in the right one. 
Some of them have an elliptical and elongated form ^ ; others are 
convex **, and it is among these latter that we must place a cele- 
brated species fFenus Dione, L., Chemn., VI, 27, 271), from whose 
form originated the application of the name Venus to the genus. 
Its transvei’se plates terminate behind in salient and pointed spines. 
There are some species of an orbicular form, and with slightly 
hooked summits, in which the impression of the retractor of the tubes 
forms a large and almost rectilinear triangle |f . 
When their animals are better known, we shall most probably 
have to separate from the Cythereae, 
1. Those species of a comjjressed lenticular form, in which the 
nates are united into a single point. The fold of the contour of the 
mantle is wanting, and shows that their tubes are not protractile : 
2. Those of a convexly orbicular form, in which the fold is not 
* These fantastic appellations of vitJva and amis, have probably caused the 
extremity of the shell, -which corresponds to the tnie anus of the animal, to be 
styled the anterior, and that where the mouth is situated, the posterior. We have 
restored to these extremities their true denominations. We must recollect that the 
ligament is always on the posterior side of the summits. 
-f- Venus Utlerata, Chemn., VII, xli ; — V. rotunda, Ib., xlii, 441 ; — V. textiKs, Ib., 
442 ; — V. decussata, xliii, 456 ; &c. 
p Venus scofica, Hans Lerin, VIII, tab. 2, f. 3 ; — Crassina danmoniensis, Lam. ; 
and among the fossil species, Ast. lucidu. Sower., Min. Conch., II, pi. 137, f. 1 ; — 
.-IsL Osmalii, Lajonkere, Soc. d’Hist. Nat.de Paris, I, tab. 6, f. 1. 
§ Venus dysera, Chemn., VI, 27, 299 ; — Ven. pticuta, Eneyc. pi. 275, 3, a, b ; — 
Ven crebisulica, Ib., f, 4, 5, 6. 
II Venus puerpera, Eneye., 27S ; — Ven. corbis, Lam., Encyc. pi. 276, f. 4. 
^ Venus gigantea, Encyc., 28,3; — Ven. chione, Chemn., VI, 32, 343; — Ven. 
erycina, Ib., 347 ; — Ven. maculata, Ib., 33, 345. 
** Ven. meretrix; — Ven. lusoria ; — Ven. castrensis. 
tt f 'enus exoletu, Chemn., VII, 38, 404 — the genus Orbiculus, Megerle. 
Ven. scripta, Chemn., VII, 40, 422. 
