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NEW YORK STATE MUSEUM 



The nepionic stage [see text fig. 25] has a very small umbilical 

 perforation, which is curved and widening outward. The ana- 

 nepionic stage is not clearly exposed, the apex of the first whorl 

 being broken off ; the metanepionic stage possesses a transversely 

 oval section with a more prominent dorsum and flatter venter [see 

 pi. 19, fig. 1] ; while in T. champlainense both are about 

 equally prominent. The siphuncle lies propioventran. In the other 

 congener it is supposed by Hyatt to be situated centren. The early 

 paranepionic stage is here characterized apparently by a still more 

 abrupt curvature than in T. c h a m p 1 a i n e n s e [see text fig. 



Fig. 25 Tarphyceras seelyi Whitf (sp.) Section 

 showing the umbilical perforation, and early whorls. 

 Natural size 



25]. Its section is kidney-shaped and shows a strong develop-) 

 ment of the impressed zone. Also the ventral saddle of the sutures 

 is already well developed. 



In the neanic stage the volution becomes higher than in the pre- 

 ceding stage, but not so rapidly and to such an extent as in T . 

 cha m plainense and the siphuncle wanders more rapidly toward 

 the center and becomes subcentren ; also the abdomen is already 

 distinctly flattened, while in T. champlainense a slight flat- 

 tening does not appear until ephebic age. In -the latter stage the 



