PLATE \l 



Platyceras dumoscm, Conrad. 



Pago 14. 



Fig. 1. View of a large ventiieoee siiecimen imbedded in i-ock, showing the form of the apertui-e and the 

 long submarginal spines in place. Schoharie. N. Y. 



Pi .MYCERAS MtJLTiBPiNOSUM, Meek. 



Page 15. 

 Figs. 2, 3. Ventral and lateral view^ i>i' a specimen communicated by Dr. J. S. Newben-y for comparison 

 with P. dwnuisum. 



