502 



NEW YORK STATE MUSEUM 



X 



\ 



with a shallow wide hyponomic sinus. Cameras very shallow, in- 

 creasing to more than double width from the earlier stages to the 

 ephebic stage ( 10 in 10 mm in nepionic stage and 4 in the same 

 space in the ephebic stage) ; sutures provided with a narrow, low 

 dorsal and a faint broad ventral saddle, in young specimens straight. 

 Septa shallow, their concavity approximately equal to the depth of 

 the cameras. 



Siphuncle large, 5 mm wide in 

 -■ - --^ the septal perforations, slightly 



contracting between the septa, pro- 

 piodorsan in position ; without any 

 organic deposits. 



Position and locality. In the 

 Fort Cassin beds at Fort Cassim 

 Observations. This interesting 

 form was referred by its author to* 

 Gomphoceras but the very slight 

 development of the lateral contrac- 

 tion of the apertural margin, dis- 

 tinctly shown in our material, 

 proves it to be of a more primitive 

 character than Gomphoceras, and 

 the Phragmoceratidae in general. 

 Hyatt has made it a genotype and 

 referred the new genus to the Oncoceratidae ; describing it as 

 consisting of exogastric forms. Since our specimens have the hypo- 

 nomic sinus on the flat or less arched side, this form seems to have- 

 relations to or could be conceived to lead to the endogastric genus. 

 Phragmoccras. 



The position of the hyponomic sinus on the flatter side indicates 

 that the animal carried the conch very much in the position given 

 to it in the lateral view [pi. 37, fig. 3]. 



Fig. 56 Cyclostomiceras c a s - 

 sinense Whitf. (sp.) Longitudinal 

 section of fragment showing the 

 living chamber, siphuncle and depth 

 of septa, x % 



Cyclostomiceras minimum Whitfield (sp.) 



Plate 35, tigure 5, 6 



Gomphoceras minimum Whitfield. Amer. Mus. Nat. Hist. BuL 

 • 1886, v. 1 , no. 8. p. 321, pi; 27, fig. 3-5. 



Observations made on specimens in the collection of Burlington- 

 University verify the statement contained in the original description,, 

 that this form had an open aperture, the margins of which were not 

 contracted. It, therefore, can not be referred to Gomphoceras but 



