45^ NEW YORK STATE MUSEUM 



tions by the different position and smaller size of the siphuncle. 

 The early appearance and disappearance of the costation on the 

 whorls suggest that it was here again in a retrogressive stage. 

 Neither the type nor any other representative of the species has as 

 yet been figured ; the specimen here reproduced, while a little more 

 imperfect in the center than the type of Billings's and Hyatt's de- 

 scriptions, is more perfect otherwise ; and we have no doubt, after in- 

 spection of the type specimen at Ottawa and the observation of 

 complete equality in the relative dimensions of the two that the 

 specific reference is correct. 



Genus eurystomites Schroder emend. Hyatt 



The genus Eurystomites has been established by Schroder [1891, 

 p. 26] to comprise forms which while in most characters like Not- 

 ling's genus Estonioceras still differ in the amount and character of 

 involution. He defines Eurystomites thus [translation] : 



" Shell completely involute. Aperture enlarged, with simple ven- 

 tral sinus. Siphuncle centriventral to ventral " ; and includes in his 

 genus Nautilus kelloggi Whitfield and N . c h a m - 

 p 1 a i n e n s i s Whitfield. Hyatt has later [1894, p. 433] separated 

 the genus Tarphyceras from Eurystomites [for differences see 

 p. 464] and referred the last cited species to his new genus. N . 

 k e 1 1 o g g i as emended by Schroder and here described is the 

 genotype of Eurystomites. 



Eurystomites kelloggi Whitfield (sp.) emend. Schroder 



Plate 17, figure i ; plate 18, figure i 



Nautilus kelloggi Whitfield (pars). Am. Mus. Nat. Hist. Bui. 1886. 



v. i, no. 8. p. 328, pi. 30, fig. t; not pi. 31, fig. 4, 5 

 Eurystomites kelloggi Schroder. Pal. Abh. herausg. von Dames 



und Kayser. 1891. B. 5, Heft -I. p. 27. 

 Eurystomites kelloggi Hyatt. Am. Phil. Soc. Proc. 1894. 



32:442, pi. 5, iig. 4, 5 



The synonymy of this species, which is the genotype of the genus 

 Hurvstomites, is extremely involved. Its original description and 

 figures contain alien elements which have been eliminated by 

 Schroder who emended the species, basing his description upon the 

 first drawing given by W hitfield [op. cit., pi. 30]. The other form 

 originally comprised under Nautilus kelloggi [pi. 31, fig. 

 4. 5 I has been described by Hyatt asE.rotundus. E . k e 1 - 

 I o g g i has not been redescribed by Hyatt. 



