270 NORTH-CAROLINA GEOLOGICAL SURVEY. 



sharp spiral ridges. These ridges are but slightly oblique to 

 the axis of the shell 



CERITHIUM BICOSTATA. N. S. (Fig. 162.) 



Shell small, thick, tapering from the base ; whirls many, 

 and ornamented with two spiral, nodulose ribs. 



TEREBELLTJM ETIWANENSIS.- TOUMEY AND HOLMES FOSSJLS OF 



SOUTH-CAROLINA. 



Shell subulate ; whirls many, pointed, flattened and orna- 

 mented with two sharp spiral ribs ; sutural line deep, especi- 

 ally below. 



This shell presents considerable variation in passing from 

 its immature to its mature state. In the young the spiral 

 ridges are placed near the suture, and the space between is 

 concave ; the waving lines of growth gives it an obscurely 

 beaded appearance. It is the most common univalve in the 

 marl beds of Edgecombe county. 



TEREBELLUM CONSTRICTUM. N. S. 



Shell rather thin terete ; whirls many convex ; lower ones 

 deeply constricted on the line of suture, and ornamented by 

 two principal raised revolving lines placed nearer the lower 

 margin than the upper ; the finer parallel lines are numerous ; 

 longitudinally,the spire is frequently marked 

 FIG. 163. k v obsolete ribs ; lines of growth indistinct. 



It differs from the T. Etiwanensis in the 

 position of the principal revolving lines, 

 and the lower rounded whirls. 



TEREBELLUM BURDENII. TOUMEY & HOLMEfl. 



FOSSILS OF SOUTH-CAROLINA, P. 122. 



(Fig. 163.) 



" Shell subulate, turrited ; whirls flatten- 

 ed, spirally ribbed and transversely striated, 

 which give the ribs a beaded character.' 7 



