GASTROPOD A—STR0PH0STYLID2E. 



68 1 



Helderbergian of New York, etc.; Oriskany of Maryland, etc. 

 236. P. ventricosum Conrad. (Fig. 957.) Devonic. 



Fig. 955. Platyceras gebhardi. 

 (After Hall.) 



Fig. 956. Platyceras gebhardi, side 

 view. (After Hall.) 



Probably derived from a Strophostyhis. Last whorl partly free, 

 and extremely ventricose. 



Helderbergian of New York, etc. Oriskany of Maryland. 

 237. P. tenuiliratum Hall. Devonic. 



FlG. 957. Platyceras ventricosum. (After Hall.) 



Like a small P. ventricosum , with reflexed inner lip, sinuous 

 margin, and surface cancellation by fine revolving and transverse 

 striae. 



Helderbergian of New York. 



Fig. 958. Platyceras multisinuatutn. (After Hall.) 



