ACEPHALA TESTACEA. 
99 . 
FAMILY IV. 
CARDIACEA. 
The mantle is open before, and there are, besides, two separate 
apertures, one for respiration, the other for the faeces, which are pro- 
longed in tubes, sometimes distinct, and at others united in one single 
mass. There is always a transverse muscle at each extremity, and a 
foot generally used for crawling. It may be considered as a general 
rule, that those which are furnished with long tubes, live in ooze or 
in sand. This mode of organization may be recognized on the shell 
by the more or less depressed contour described by the insertion of 
the edges of the mantle previous to its uniting with the impression of 
the posterior transverse muscle*. 
Cardium, Lin., 
The Cardia, like many other bivalves, have an equivalve, convex 
shell, with salient summits, curved towards the hinge, which, when 
viewing it sidewise, gives it the figure of a heart ; hence its name of 
Cardium, heart, &c. Ribs, more or less elevated, are regularly dis- 
tributed from the summits to the edges of the valves ; but what 
chiefly distinguishes the Cardia, is the hinge, through which, in the 
middle, are two small teeth, and at some distance before and behind 
a projecting tooth or plate. The animal, — Cerastes, Poll, — has ge- 
nerally an ample aperture in the mantle, a very large foot forming an 
elbow in the middle and with its point directed forwards, and two 
short or but moderately long tubes. 
Numerous species of Cardia are found on the coast of France, 
some of which are eaten, such as the 
C. edule, L. ; Chemn., VI, xix, 194. Fawn-coloured or 
whitish with twenty-six transversely plicated ribs. 
Under the name of Hemicardium, we might separate those species 
in Avhich the valves are compressed from before backwards, and 
strongly carinated in the middle; for it seems almost certain, that 
a modification of the animal must be a necessary consequence of tliis 
singular configuration!. 
Don AX, Lin., 
The Donaces have nearly the same kind of hinge as the Cardia, but 
* They form the family of the Conchacea, Blainv. 
-f- Cardium Cardissa, VI, xiv, 143 — 146; — Card, roseum, Ib., 147 ; — Card, mon- 
strosum, Ib. 149, 150; — Card, hemicardium, Id., xi, 159 — 161. 
The other Cardia of Gmelin may remain where they are, the C. gaditanum excepted, 
which is a Pectunculus. There are several fossil species described by Messrs. Lamarck, 
Brocchi, and Brongrniart. 
H 2 
