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ISCCARDIA. Ta Marck. 
Gen. Cuar. An equivalved cordiform bivalve, with 
distant involute beaks ; teeth of the hinge two, 
compressed, one of them curved under the 
beak ; one lateral tooth extended beneath the 
lunette ; ligament external, anteriorly furcated. 
Iw several positions the shells of this genus present a 
cordiform outline, because they are generally very gib- 
bose, and the notch in which the hinge is imbedded is 
very large; the incurved beaks assist greatly in distin- 
guishing them when the hinge teeth cannot be examined, 
as is often the case in fossils. Chama Cor of Linneus 
is the type of the genus. ; 
ISOCARDIA minima. 
TAB. CCXCV.—Fig. 1. 
Spee. CHar. Globose, subdeltoid; anteriorly 
slightly truncated, posteriorly flattened; cordate. 
Tue flat heartshaped posterior side of this shell distin- 
guishes it from Tsocardia Cor which otherways it re- 
sembles except in size, being much smaller, the anterior 
side is sharply produced a little way and slightly trun- 
cated. 
I have only met with casts of this shell which do not 
exhibit the hinge teeth, and are besides rather rugged, 
but no better are likely to be found. 1 am indebted to 
Mr. Salmon for them; they were collected in Wiltshire, 
probably in the Cornbrash Limestone. T have similar 
ones from Madagascar. 
ISOCARDIA tener. 
TAB. CCXCV.—F'%g. 2. 
Sprc. Cuar. Obovate, with produced beaks ; 
anteriorly subtruncated, posteriorly rounded ; 
shell very thin, smooth. 
Ax elegant thin shell, rather wider than long, with a 
straightish front; it is less gibbose than the last, and the- 
i) es lie 
