2T6 NORTH-CAROLINA GEOLOGICAL SURVEY. 



C. DUMOSUM. 



Shell depressed, sub-conical, oblong or oval at base ; sur 

 face ornamented with spiral ribs, and whose spines are hol 

 low. 



C. MULTILINEATTIM. (Fig. 192.) 



Shell rather small, depressed, very thin ; apex elevated, 

 sub-central, disk marked with radiating lines. Rather com 

 mon in the miocene. Usually occupies the interior of other 

 shells. 



TKOCIIITA CENTRALIS. (Fig. 193.) 



Shell rather small, very thin, round, ovate ; apex medial 

 minutely spiral and acute. Associated with the foregoing 

 shells of this family. 



CREPIDTJLA. LAM. 



Crepidula has the limpet shape, but a posterior oblique 

 marginal apex. Interior has a horizontal plate, forming a 

 partition which curves the posterior half. They vary in form, 

 which is very much dependent upon the surface to which they 

 are attached. 



CREPIDULA FORNICATA. (Fig. 194.) 



Shell obliquely oval ; surface convex, smooth or wrinkled ; 

 apex turned to one side : diaphragm concave below, occupy 

 ing half the shell. Common in the miocene of North-Caro 

 lina. 



CREPIDULA SPINOSA. 



Shell depressed, oval, costate and spinous, especially to 

 wards the margin. Common in the miocene. 



CREPIDULA PLANA. SAY. (Fig. 195.) 



Shell nearly flat, slightly convex ; diaphragm convex ; the 

 form is very variable, assuming the shape of the surface upon 

 which it rests. 



