GASTROPODA— STROPHOSTYLID&. 



685 



General form as in P. bucculentum, but apex merely incurved 

 instead of enrolled. 



Kinderhook of Iowa ; Waverly of Ohio. 

 253. P. tribulosum White. (Fig. 967.) Mississippic. 



Fig. 965. Plalyceras nodosum, mold of a large scarcely coiled form. (After Hall.) 



Similar to preceding, with strong sinuosities in lip, and three 

 rows of hollow spines. 



Burlington of Iowa and Missouri. 

 254. P. haliotoides Meek and Worthen. (Fig. 968.) 



Mississippic. 



Fig. 966. Platyceras Jumosum, X Z A- (After Hall. ) 



