468 NEW YORK STATE MUSEUM 



The dorsal saddle remains low and broad also in the ephebic stage. 



The surface has been observed in the neanic and ephebic stages. 

 In both of them fine growth lines, very often but ndt regularly in- 

 terrupted after each fifth or sixth line by a stronger one, were ob- 

 served. They indicate a sharp hyponomic sinus, the depth of which 

 in the neanic stage is about ecjual to that of a chamber. The low 

 costae observed by Hyatt on the ananeanic stage of T . c h a m - 

 plainense do not seem to appear upon the conch of this species. 



The differences in the development of the conchs of T. cham- 

 plainense and T . s e e 1 y i consist principally in the earlier ap- 

 pearance (and stronger development) of the ventral flattening and 

 the earlier and more rapid turning of the siphuncle toward the 

 center in the latter. The ephebic and gerontic volutions of the two 

 forms differ principally in the development of later zones in T . 

 seelyi, for though in the original description of the species it is 

 stated that a section of the tube is nearly a circle, T . c h a m - 

 plainense is described as different from T . seelyi in being 

 less compressed laterally. 



We give here [pi. 21, fig. i] the outline of a very large speci- 

 men with a diameter of 175 mm which shows that even in the 

 gerontic stage the last volution does not uncoil. The living chamber 

 in this specimen occupies about ^ volution. The aperture had a 

 deep hyponomic sinus but seems to have lacked any larger expan- 

 sion and possessed but very low lateral crests. 



Position and localities. At Valcour this species has been found 

 in the beds A3 and A5 of the section. Its original locality is at 

 Fort Cassin Vt. 



Tarphyceras champlainense A^Hiitfield (sp.) 



Nautilus ? champlainensis Whitfield. Am. ]Mus. Nat. Hist. 



Bui. 1886. 1:329, pi. 31, fig. I, 3 

 Eurystomites champlainensis Schroder. Pal. Abhandl. 1891. 



Bd. 5, Heft 4, p. 28 

 Tarphyceras champlainense Hyatt. Am. Phil. Soc. Proc. 



1894. 32:438, pi. 4, fig- 4-1 1- 



The description and figures of the mature form of T . c h a m - 

 plainense by Whitfield and the very extensive illustration 

 and description of the ontogenetic stages of the same by Hyatt do 

 not require any further descriptive remarks upon this species which, 

 moreover, has not been observed in any other place but at Fort 

 Cassin, the original locality, or seen in better specimens than those 

 which have before been described and figured. 



