44 NOMENCLATURE. 



posticus. Posterior ; next the areola, 

 complicatus. Complicated j membranaceous, 



forming an acute angle. 

 diipUcatus, Duplicate; deeply cleft, as it were 



bifid. 

 depressus. Depressed; turned inward. 

 erectus. Erect; perpendicular to the plane of 



the hinge. 

 longitudinalis. Longitudinal ; produced along 



the margin. 

 maslicans. Articulate; furnished with many 



teeth, so situated that when the valves are 



closed they lock into each other. 

 primarius seu 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 ScroUculus have nearly the 



same signification. 

 Intestinum. Intestinal ligature ; a memr 



branaceous tube by which some of the 



