FOSSILS OF THE NIAGARA GROUP. 



405 



GENUS PHRAGMOCERAS, Broderip. 



PhRAGMOCEBAS NESTOR, N. S. 



A fragment preserving the outer chamber and several of the septa, is 

 ventricose, broadly expanded in the dorso-ventral direction, and measur- 

 ing from the extreme limits of the apertures, which are marginal, more 

 than two and a half inches ; the length of the narrow constriction 

 between them being one inch and a quarter. Both the dorsal and ven- 

 tral apertures are marginal and expanded. 



The length of the outer chamber along the middle is an inch and 

 three-fourths, and the dorso-ventral diameter in the middle of the leneth 

 is two and a quarter inches. The septate portion has been abruptly 

 arcuate, the length of the part remaining being four times as great on 

 the outer as on the inner side of the curve. The greater and lesser 

 diameters of the septa are about as seven to ten. The siphuncle is sub- 

 marginal. 



The cast of the outer chamber is marked by what appears to be regu- 

 lar vascular impressions extending outwards from the first septum. 



In fig. 3 a lateral view is given of the specimen described, and in fig. 4, 

 a view of the aperture. 



Fig. 3, 



Fig 4 



This species differs from the P. hector, Billings, of the Guelph lime- 

 stone of Canada, in being more narrowly elliptical in section, and much 

 more expanded in the dorso-ventral direction at the aperture, as well as 



