30 NEW YORK STATE MUSEUM 



to be to a large degree the cause of the irregularities in contour often 

 displayed by full-grown shells, the smaller form has these concentric 

 growth lines more sharply denned and elevated, and these are covered 

 ' by equally fine and sharp interrupted revolving striae, which together 

 produce an effect similar to that exhibited by the common Hamilton 

 species, D. lineatum Conrad. These revolving lines seldom cancellate 

 the concentric erect lines, but profoundly modify their interspaces. 



In general form these shells do .not widely differ from the early 

 whorls of D. ventricosum, but their abundance and uniformity of 

 size in addition to the characters indicated seem to establish a specific 

 difference. 



Diaphorostoma ventricosum Conrad 



Plate 3, flg. 25-28 



1892. Diaphorostoma ventricosum Clarke, op. cit. p. 412 



For other figures see Paleontology of New York. v. 3, pi. 112, fig. 

 1-10; 113, fig. 7, 8; 115, fig. 8 



This species is the most abundant of all the gastropods and attains 

 normal size and proportions, though usually the large ventricose body 

 whorl has been crushed. 



Strophostylus expansus Conrad 



Plate 3, flg. 24 



1892. Strophostylus expansus Clarke, op. cit. p. 412 



For other figures see Paleontology of New YorJc. v. 3, pi. 114, fig. 2, 3a, b 



A single well defined example of this shell has been observed. 



Orthonychia tortuosa Hall 



1892. Platyceras tortuosum Clarke, op. cit. p. 412 



For figures see Paleontology of New York. 3:472, pi. 113, fig. 1-5 



This species is not common, and no well-preserved examples have 



been seen. 



Platyceras cf. gebhardi Hall 



Plate 3, flg. 99 



Platyceras gebhardi 1 was described from the Oriskany of 

 'Paleontology of New York. 3:474, pi. 117, fig. 1-10. 



