NOMENCLATUKE. 
27 
depressus. Depressed ; having a simple tooth ex- 
tending the hinge towards the anterior part. 
excisus. Cleft ; gaping with a transverse slit, 
longitudinalis. Longitudinal ; running nearly the 
whole length of the shell, 
lateralis. Lateral ; projecting on either side. 
rejiexus. Reflex; bent or folded over the exte- 
rior margin. 
terminalis. Terminal ; placed at the extremity of 
the shell. 
truncatus. Truncate ; having the beaks trans- 
versely cut off, and the hinge placed within 
them. 
Costa cardinis. Hinge rib ; an elevated line run- 
ning from the hinge internally to the infe- 
rior margin. 
Cicatrix. Cicatrix; internal muscular im- 
pression. 
Dens. Tooth; an acute projection within the 
hinge, by which the valves are united and 
often articulated, 
anticus. Anterior; the tooth nearest the liga- 
ment, or on the side of the area. 
