CHAMIDA, 197 
The curious history of the genera of this family, and of the 
many conflicting views of their extent and relationships, is ably 
given by Prof. Angelo Heilprin in Proc. Acad. Nat. Sciences, 
Philad., 423, 1881. 
VERTICORDIA, Searles Wood, 1844. 
KHtym—Verticordia, a name of Venus. 
Syn. —Trigonulina, d’Orb. 
Distr.—3 sp. China Sea, Mediterranean ? Fossil, 2 sp. Mio- 
cene—; Britain, Sicily, North Carolina. V. cardiiformis, Wood 
(cxxv, 26). 
Shell suborbicular, with radiating ribs; beaks subspiral ; mar- 
gins denticulated ; interior brilliantly pearly; hinge with one 
prominent cardinal tooth in each valve; adductor scars two, 
faint; pallial line simple; ligament internal, oblique; epidermis 
dark brown. 
PrccutoLta, Meneghini, 1851. 
Distr.—3 sp. N. Europe. VP. argentea, Meneg. Miocene; 
Kurope. 
Shell suborbicular, equivalve, strongly ventricose, with the 
beaks incurved and distant from each other, surface radiately 
sulcated and ribbed ; hinge in the right valve with a strong car- 
dinal tooth below the umbo, a corresponding indentation in the 
left valve; ligament apparently linear, situated along the upper 
posterior margin. 
ALLopaaus, Stoliczka, 1870. 
Syn.—Hippagus, Deshayes, non Lea, 
Distr.— Hippagus Leanus, Deshayes (exxvii,60 . Paris Basin. 
Shell ovate, thin, very inequilateral, moderately tumid, with 
small approximate beaks; surface smooth with simple striz of 
increase ; right valve with one tooth in front of the umbo, left 
with a similar tooth below the umbo; ligament subinternal, pos- 
terior. 
The type of this group is Hippagus Leanus, Deshayes. The 
species differs by the hinge and the structure of its shell from 
Hippagus, Lea’s original figure of H. isocardoides being appar- 
ently quite correct—the latter group belonging to all appearances 
close to Mysia in the Ungulinide. Deshayes’ species is exter- 
nally very like a Mytilimeria, but this again accords in the char- 
acter of its hinge with true Hippagus. 
( Chamacea.) 
Faminy CHAMID A. 
Shell inequivalve, thick, attached ; beaks subspiral; ligament 
external ; hinge-teeth two in one valve, one in the other; adductor 
impressions large, reticulated ; pallial line simple. 
