CORBULACEA. 99 
cylindrical, equivalve, very inequilateral; umbones slightly 
raised and quite anterior; hinge nearly the same in both valves ; 
two small cardinal teeth, one of which is bifid, placed before a 
kind of lamellar tooth, beneath a very slender external liga- 
ment; two small, rounded, distant, muscular impressions, uni- 
ted by a straight palleal impression, which is strongly sinuated 
posteriorly. Obs. This shell, which is found in the empty holes 
of dead Lithodomi, in some instances conforming its shape to its 
situation, differs from Cypricardia of Lam. principally in its 
cylindrical form. C. Carditoidea, fig. 92. 
CORBI'CULA. Megerle. Cyrena, Lam. 
COR’BIS. Lam. (A basket.) Fam. Nymphacea, Lam. Descr. 
Transverse, oval, thick, ventricose, equivalve, sub-equilateral, 
free, cancellated, with denticulated internal margins; hinge with 
two cardinal and two lateral teeth ineach valve; of the latter, 
one near and one remote from the umbones; muscular impres- 
sions lunulate, two in each valve, united by an entire, unsinuated, 
pallealimpression. Obs. This genus, of which only one recent 
species is known, resembles many species of Venus and Cythe- 
rea, in general form; but differs in having lateral teeth, and in 
the palleal impression, which in all the Veneres, &c. is sinuated. 
From Lucina it may be known, not only by its oval form, but 
also by the muscular impressions, which in Lucinaare produced 
into an elongated point; it will also be distinguished from 
Tellina, by the want of a posterior fold in the valves, for 
which that genus is remarkable. C. Fimbriata, fig. 101, is an 
inhabitant of the Indian Ocean. Several fossil species are 
found in the recent formations, above the chalk, at Grignon and 
Granville. 
COR’BULA. Lam. (A little basket.) Fam. Corbulacea, Lam. 
Conchacea, Bl. Descr. Inequivalve, sub-equilateral, transverse, 
gibbose, not gaping; cardinal tooth in each valve, conical, 
curved, prominent, inserting its extremity intoa pit in the oppo- 
site hinge; cartilage attached to the tooth of the smaller valve, 
and the pit in the larger; muscular impressions two in each 
valve, distant, rather irregular; impression of the mantle pos- 
teriorly angulated. Obs. ‘The shells composing this genus were 
placed in Mya by Linneeus, but differ from the true Mye in 
having a sinus in the palleal impression, and a prominent liga- 
mentiferous tooth in each valve, whereas the Myz have but 
one. The Corbulz are marine, some species inhabiting the 
British coasts. Fossil species occur abundantly in green sand, 
London clay, Crag, and corresponding formations. Fig. 89. 
C. Nucleus. 
CORBULA’CEA. (Corbulées, Lam.) <A family of the order 
Conchifera Dimyaria, Lam. containing the genera Corbula and 
Pandora, fig. 89, 90. 
