28 NOMENCLATURE. 



posticus. Posterior ; next the areola. 



complicalus. Complicated; membranaceous, form- 

 ing an acute angle. 



duplicatus. Duplicate; deeply cleft, approaching 

 to bifid. 



depress7is. Depressed ; turned inward. 



ereclus. Erect ; perpendicular to the plane of the 

 hinge. 



longihidinalis. Longitudinal j produced along the 

 margin. 



masticans. Articulate ; furnished witli many teeth, 

 so situated that when the valves are closed 

 they lock into each other. 



primarius sen cardinalis. Primary or Cardinal; 

 situated between the beaks. 



Discus. Disk; the middle of each valve, the 

 convex part between the bosses and the 

 margin. 



FossULA. Sinus; a small hollow in the hinge. 

 Foveola and Scrohiculus have nearly the 

 same signification. 



Intestinum. Intestinal ligature ; a mem- 

 branaceous tube by which some of the 



