GASTROPODA— BELLEROPHONTIDJE. 



617 



Rockford limestone of Indiana, Kinderhook of Iowa, Marshall 

 of Michigan, and Waverly group of Ohio. 



Fig. 827. Oxydiscus curvilineata. (After Hall.) 



XVIII. Phragmolithes Conrad. {Conradella U. and S.) 

 Differs from the preceding in the absence of marginal angular 

 sinus and in the coarsely wrinkled lamellose growth lines. Slit 

 generally long, aperture expanded. Ordovicic. 

 48. P. triangularis U. and S. (Fig. 828, a t b.) Ordovicic. 



a, b, Phragmolithes triangularis ; c, d, P. fimbriatus ; e, f y P. dyeri 



FIG. 828 



(/, enlargement of surface) 



(After Ulrich and Scofield, Pal. Minn/ 



Readily distinguished by its rather rapidly enlarging volutions 

 of strongly triangular section and abrupt inflection at the um- 

 bilicus. 



Stones River of Minnesota, Wisconsin, Illinois and Tennessee. 



49. P. fimbriatatus U. and S. (Fig. 828, c, d.) Ordovicic. 

 Rounded whorls sharply carinate and with periodically expand- 

 ing lip, leaving numerous strong imbricating growth lamellae. 



Stones River group of Minnesota and Illinois. 



50. P. compressus Conrad. Ordovicic. 

 Volutions scarcely contiguous, rounded, and sharply and pro- 



