BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 465 



Tarphyceras farnsworthi (Billings (sp.) pars) Hyatt emend. 



Lituites farnsworthi Billings (pars). Pal. Foss. 1861. 1:21 

 Tarphyceras farnsworthi Hyatt. Am. Phil. Soc. Proc. 1893. 



32:43s 



Hyatt, while investigating the nautiloid cephalopods, found that 



Billings's species Lituites farnsworthi from the Beekman- 

 town formation at Philipsburg on Missisquoi bay of Lake Cham- 

 plain, consisted really of several distinct species, one of which he 

 referred to Tarphyceras and two others to the genus Aphetoceras 

 (A. farnsworthi and A . a t t e n u a t u m ) . 



The first species is described by him as follows : 



It has an elliptical or oval whorl in the ephebic stage, the dorsum 

 a little broader than the venter. There is a contact furrow in 

 the neanic and ephebic stages. The sutures have ventral saddles, 

 with probably slight dorsal lobes in the zone of involution, and a 

 free living chamber over one half of a volution in length. The 

 siphuncle is subventran in the ananeanic substage, becoming pro- 

 pioventran in the paraneanic and ventrocentren in the metephebic 

 substage. The diameter of the largest specimen, somewhat com- 

 pressed, was 140 mm by 146 mm ; the estimated longest diameter 

 of this through the free living chamber was about 160 mm. 



Tarphyceras seelyi Whitfield (sp.) 



Plate ig, figure j, 2 ; plate 20, fijjure 5 ; plate 21 ; plate 24, fiigure 3 



Lituites seelyi Whitfield. Am. Mus. Nat. Hist. Bui. 1886. v. i, no. 8, 



P- 330, pi. 31, fig- 2; pi. 32, fig. 3 

 Tarphyceras seelyi Hyatt. Am. Phil. Soc. Proc. 1894. 32:435. 



The mature stage of T . seel y i has been described very care- 

 fully by the author of the species. This type belongs evidently to the 

 more common and characteristic forms of the beds at Fort Cassin ; 

 and is also well represented in the corresponding beds at Valcour. 

 In referring to the original description we will only state that, in 

 a general Avay, the species is characterized by the small rate of 

 growth and the subcircular section of the volution, the small amoimt 

 of involution and the subcentral position of the small siphuncle. 

 The septa are closely arranged and c|uite concave. 



The ontogeny of the species has not yet been investigated, or at 

 least described, while that of the very similar T . c h a m p 1 a i n - 

 c n s e has become Avell known by Hyatt's researches. One of our 

 specimens retained the early volutions so well preserved that we 

 were able to break out the first whorls successively and thus obtain 

 the characters of the nepionic and neanic growth stages. It may be 

 stated that they are also similar to those of T. c h a m p 1 a i n e n s e . 



