147 
PERNA, De Lamarcke, &c. 
Gen, Cuar. Subequivalved oblique winged bi- 
valve, hinge formed of many parallel linear 
teeth, not articulating, and ranged upon a 
straight, transverse, or oblique line. Ligament 
attached between the teeth on each valve. 
ra 
Tue Genus Crenatula (Parkins. Org. Rem.) is somewhat 
related in respect to the crenulated hinge, but is otherwise 
yery distinct, These will require further attention. 
PERNA aviculoides. 
TAB. LXVI. 
Spec. Cuar. Depressed, very oblique, ovato- 
lanceolate, wings small, beak straight; lines of 
growth fine, prominent, sharp. 
Leneru equal to thrice its breadth, the posterior wing is 
sharp; the hinge straight; anterior wing very obtuse, and 
the front round; sometimes six inches long. 
This species has been found frequently in various im- 
perfect states of preservation, in which it has been difficult 
to gain proper instruction as to where to place it syste- 
matically, and although in its general construction it is 
sufficiently distinct, and its peculiarities convenient, as far 
as we know them, yet its generic and essential characters 
are concealed. 
