NOMENCLATURE. 25 



BIVALVES. 



Ambitus, Circumference of the shell. 



Area. Slope. 



antica. Anterioi' slope or Area ; that side of the 



beaks or that space in which the ligament 



is situated. 

 distincta. Distinct; separated from the sides of 



the shell either by a channel or a keel. 

 iujiexa. Inflex : having incurved lips, 

 literata. Literate; ornamented with characters 



like letters. 

 postica seu Areola. Posterior slope; the other 



side of the beaks. 

 marginata. Marginate; surrounded by an ele- 

 vated margin. 

 patula. Patulous; the margins of the areola 



gaping, 

 serrata. Serrate ; saw-like in the channel of the 



areola. 

 Apices. Beaks; the tips or extreme parts of 



the umbones or bosses. 



