CARDIID. 193 
CARDIUM, restricted. (Tropidocardium, Rémer.) Shell ven- 
tricose, subeqilateral, more or less gaping behind; margin 
strongly dentate; valves covered with strong radiating ribs. 
C. costatum, Linn. (exvi, 70). 
BUCARDIUM, Gray. (Pectunculus, Adanson.) Shell globose, 
solid, strongly ribbed, the ribs produced on the gaping posterior 
margin into strong spine-like teeth. C. ringens, Chemn. (exvi, 
14). 
TRACHYCARDIUM, Morch. (Granocardium, Gabb.  Criocar- 
dium, Conrad, 1870.) Shell oblong, inflated, a little oblique, 
radiately ribbed ; the tops or sides of the ribs scaly spinose. C. 
muricatum, L. (exvi, 72-74). West Indies. Fossil. Cret.; 
California. Criocardium is ‘‘ Multiradiate, interstices spinose, 
ribs smooth; anterior lateral tooth long and prominent.” C. 
dumosum, Conr. Cret.; N. Jersey. The spines originate later- 
ally on the ribs (as is not unusual in the genus), and not 
between them. 
ACANTHOCARDIA, Gray, 1847. (Isocardia, Klein.) Shell sub- 
globose, radiately ribbed, the ribs bearing strong, sharp, curved 
spines. C.aculeatuwm, Linn. (exvi, 75). 
CERASTODERMA, Poli, 1791. Shell subcordiform, rounded 
behind; valves close, flatly ribbed; cardinal teeth strong. C. 
edule, Linn. , cxvi, 76). 
PAPYRIDEA, Swains., 1840. Shell oval, oblong or transverse, 
thin, inequilateral; radiately ribbed, the ribs forming strong 
marginal teeth posteriorly. C. hiulea, Reeve (exvi, 77). 
FULVIA, Gray, 1847. Shell transversely oblong, very inequi- 
lateral, posteriorly produced, radiately ribbed. Differs very little 
from the last group. C. bullata, Linn. (exvi, 78). 
LYMNOCARDIUM, Stol., 1870. (Pseudocardia [part], Conrad, 
1866. Vetocardia [part], Conrad, 1868.) Shell elongated, 
inequivalve, with the anterior side shorter, moderately inflated 
and rather thin, surface radiately ribbed ; cardinal teeth two, or 
one in each valve, small, and sometimes quite obsolete, lateral 
teeth remote, more or less lamelliform, pallial line either entire 
or (rarely) sinuated, posterior gape usually distinct. Type, 
Cardium Haueri, Hornes. The species are Tertiary; Eastern 
Europe, W. Asia. The type is one of the species which Conrad 
quotes under his genus Pseudocardia, the name of which the 
same author subsequently replaces by Vetocardia. When giving 
the characteristics of the latter, he evidently refers solely to 
d’Orbigny’s cretaceous Venericardix, but how it was possible to 
associate with these forms the first named ones and others 
described by Hérnes from the uppermost tertiary beds of the 
Vienna (or rather Hungarian) Basin, it is really difficult to 
understand, and this the more when, after the enumeration of 
