NOMENCLATURE. 4S 



nished with various protuberances and hol- 

 lows. 

 depressus. Depressed ; having a simple tooth ex- 

 tending the hinge towards the anteriorpart. 

 excisus. Cleft ; gaping with a transverse slit. 

 longitudinalis. Longitudinal; running nearly 



the whole length of the shell. 

 lateralis. Lateral ; projecting on either side. 

 rejlexus. Reflex ; bent or folded over the ex- 

 terior margin. 

 terminalis. Terminal; placed at the extremity 



of the shell. 

 iruncatus. Truncate ; having the beaks trans- 

 versely cut olf, and the hinge placed with- 

 in them. 

 Costa cardints. Hinge rib ; an elevated line run- 

 ning from the hinge internally to the infe- 

 rior margin. 

 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. 



