13 
GERVILLIA, Defrance. 
Gen. Cuar. An unequal-valved, unequal-sided bi- 
valve, oblique, much elongated ; beaks near 
the anterior extremity ; hinge long ; divided 
into several pits, and furnished with many, more 
or less lamelliform, teeth ; one muscular im- 
pression in each valve. 
A cenvs nearly related to Perna.. The species upon 
which it is founded has nearly parallel edges ; but seve 
ral others that possess the same characters in the hinge, 
are ovate, and more or less taper towards the extremi- 
ties. The hinge consists in a long transverse area, con- 
taining 3 or more shallow hollows destined to receive 
the ligament; about the inner edge of this area are a 
number of irregular interlocking lamellar teeth, varying 
in their direction and size in different parts of the same 
hinge and in different species ; those placed towards the 
anterior extremity are, in the type of the genus, small 
and longitudinal; the others long and transverse: in other 
species they are all either oblique or transverse. The 
casts of the typical species indicate a shell that gapes at 
one if not at both extremities ; the other species are close. 
The shell in all is thick, and probably consists chiefly of 
earl. 
$ Mons. Defrance established this genus in the Diction- 
naire des Sciences Naturelles, from casts discovered by 
Mons. de Gerville,—in commemoration of whom he has 
named it, and thus done honour toa Naturalist whose zeal 
and urbanity justly merit it.—Other species have been 
added to it by Mons. Eudes-Deslonchamps, in conse- 
quence of the resemblance in their hinges. Hereafter 
these will form at least a sub-genus. 
18; & - 
