Lamarck’s Genera of Shells. 315 
Most of the cardiacea are ventricose shells; almost all are 
furnished with radiating longitudinal ribs, and when viewed at 
the fore part, are heart-shaped. They are amie regular, 
and sometimes gaping. 
1. Cardium *. 
Shell equivalve, subcordate; beaks prominent; valves in- 
dented, or plicate on the internal margin. Hinge with four 
teeth on each valve, namely, two cardinal, approximate and 
oblique, articulating crosswise with the corresponding teeth 
of the other valve; and two lateral teeth, distant, entering. 
The prominent cordate beaks of the shells of this genus, 
first established by Linnzeus, are very remarkable. The convex 
side of the valves is generally furnished with longitudinal ribs, 
more or less prominent, frequently striated, imbricate, or spinous ; 
but their interior is smooth, and only furrowed towards the 
margin. Theligament is external, and very short; there are 
two faint muscular impressions. 
The animal projects two unequal tubes from one side of the 
shell, in general shorter than those of the conche, and tellinaria, 
and fringed at their orifice ; from the other side a large mus- 
cular falciform foot. It is said that some species spin a sort of 
byssus when they wish to fix themselves to marine substances. 
The cardia generally live buried in the sands near the coasts. 
They are found in all seas, and some of the European fossil spe- 
cies are now only known in the recent state in the Asiatic ocean. 
The species are subdivided into (1) shells which have no par- 
ticular angle on the beaks, and whose anterior margin, is, at 
least, as large as the posterior,—38 species. (2) Shells whose 
beaks are carinate, or furnished with an angle, and whose pos- 
terior margin is often larger than the anterior. 10 species. 
Type. Cardium costatum+. (Idem. Linn.) 
Shell ventricose, subglobular, subequivalve; ribs prominent, 
carinate, concave; anterior side gaping. 
African seas. In all 48 recent species, and 14 fossil. PI. vi. 
Fig. 59. 
*From xaedie, cor, a heart. t Ribbed, 
