32 NOMENCLATURE. 



dor sat a. Dorsal ; the back obtusely keeled. 



edentula. Toothless, with reference to the mar- 

 gin. 



hians. Gaping; the valves so partially closing, 

 that the margins do not every where touch 

 each other. 



infiexa. Inflex ; bent towards the anterior slope. 



linguiformis. Linguiform ; tongue-shaped, linear 

 with the extremities obtusely rounded. 



navicularis. Navicular; boat-shaped. 



pectinata. Pectinate ; longitudinally sulcate or 

 striate ; the striae forming an acute angle 

 in the anterior part. 



radiata. Radiate; with diverging rays flowing 

 from the apex longitudinally to the cir- 

 cumference. 



rostrata. Rostrated ; the anterior extremity elon- 

 gated and narrowed. 



J'astigiata. Fastigiate ; terminating transversely 

 at the base. 



saccata. Saccate ; distended towards the beaks. 



tnmcata. Truncate ; part of the circumference 

 being abrupt, or, as it were, cut off. 



