105 
VENERICARDIA. La March . 
Gen. Char. An equalvalved, inequilateral bivalve; 
ribbed longitudinally, hinge furnished with 
two thick teeth directed obliquely to one side. 
A. genus of shells externally much resembling* Car- 
dium, but with a totally different hinge, which consists 
of two teeth in one valve fitting into hollows in the 
other, they both rise near the beaks, and are nearly 
parallel with each other and the hinge slope ; one is 
generally shorter than the other, and takes a more lon- 
gitudinal direction ; the longer one is often compara- 
tively thin, and sometimes it is lost in the callosity that 
supports the cartilage. 
VENERXCARDIA senilis. 
TAB. CCLVIIX. 
Spec. Char. Obliquely cordate, thick, with large, 
convex, subimbricated, naked ribs ; lunette 
obsolete. 
Syn. Yenericardia senilis. Dc La March , Env. 
de Paris , 222. Parkinson , 3, 191, t. 13, 
jigs. 15 and 17. 
By age this shell becomes transversely oblong, and 
when young it has somewhat of a square form produced 
by the elevation of the hinge slope ; the ribs are about 
17 in number ; they are rather rugose in consequence 
of the edges of the imbrications being blunt and seldom 
reflected ; the edge has a square tooth between each rib 
as is common in Cockles, Pectens, &c. 
Fig. 1 represents a well grown individual of this 
species, and fig. 3 a younger one. 
Fig- 2 is a thick variety, and seems to have been 
interrupted in its growth, having lived in a less conge- 
nial soil ; it has been thought to be a distinct species, 
and the Rev. Mr. Leathes, to whom I am indebted for 
it, proposes to call it Yenericardia antiquata. 
They are all from the Suffolk Crag. 
