7H 



NORTH AMERICAN INDEX FOSSILS. 



Chipolan of Gulf States ; St. Mary's and Calvert formations of 

 Maryland ; Miocenic and Pliocenic of Virginia, the Carolinas, etc. ; 

 modern seas. 

 363. C. fornicata (Linne). (Fig. 1031, c, d.) Miocenic-Recent. 



Fig. 103 1, a, b, Crepidula plana, nat. size; c, d, C. fornicata, enlarged. (Md. 



Survey. ) 



Convex, with enrolled apex, and deep-set platform. 

 Widely distributed in marine Miocenic and Pliocenic of America 

 and abundant on modern coasts. 



CX. Crucibulum Schum. 



Patelloid shells with coiled protoconch and strongly expanding 

 body whorl. Platform deeply concave, producing the cup and 

 saucer aspect. Tertiary-Recent. 

 364. C. chipolanum Dall. Oligocenic. 



Like C. auricula, but radiating striae sharply cut and stronger, 



a -se^ b 



Fig. 1032. a, b, Crucibulum costatum, X 2 />> '■> c ~ e t & pilcolum ; c, young, X l H » 

 d, e, adult, X %- ( Md - Survey.) 



though not as strong as in C. pileolum ; rarely dichotomous. 



Chipolan of Gulf States. 

 365. C. costatum (Say). (Fig. 1032, a y b.) Miocenic. 



Mostly smooth, with faint costae near margin, cup attached on 

 one side. 



