4o8 



NEW YORK STATE MUSEUM 



species from the " Quebec group " of Newfoundland. The greater 

 rate of growth of the conch, closer arrangement of the septa, smaller 

 size and different position of the siphuncle in the Newfoundland 

 form forbid, however, this identification; while on the other hand 

 these smaller fragments correspond in their rate of growth, relative 

 size and position of the siphuncle and the undulating character of 

 the sutures sufficiently well with C . b r a i n e r d i to permit their 

 reference to that species. It is true the depth of the chambers is in 

 the large type of C . b r a i n e r d i and the fragments in question 

 nearly the same, but since also other forms show sometimes hardlv 

 any increase in chamber depth with advancing age, it is not neces- 

 sarily to be inferred that the later growth stages of the fragments 

 must have possessed deeper chambers. 



Cameroceras tenuiseptum Hall (sp.) 



Plate 3, figure i, 2 ; plate 4, figure 1 ; plate 5, figure 5, 6 ; plate 6, figure 2 



Orthoceras tenuiseptum Hall. Pal. N. Y. 1847. 1 135. pi. 7, 

 fig. 6 



Orthoceras tenuiseptum Raymond. Am. Pal. Bui. 1902. v. I, 

 no. 14, p. 19 



The original description of this species is : 



Cylindrical, gradually tapering, straight ; surface smooth ; section 

 cylindrical; septa very thin, gently arched, approximate about 1/25 

 the diameter ; siphuncle small ? 



Only fragments of this shell have been found in this limestone, 

 and therefore all its characters can not be ascertained. It corre- 

 sponds in many respects with O . primigeniu m of Vanuxem 

 [pi. 3, fig. 11] ; but the specimens of that fossil attain only a small 

 size, while this one is very large. Another difference will be ob- 

 served in the concavity of the septa, which are less arched in the 

 specimen under consideration. 



Position and locality. Chazy, Clinton CO., in the dark limestone, 

 associated with M a c 1 u r e a m a g n a . The specimens appear on 

 the surface of the strata, and are all more or less weathered. 



The description and the figure of the type which is deposited in 

 the New York State Museum [no. 4026 of type catalogue] show 

 that this species has been based upon the oblique section of a 

 fragment, which fails to show either siphuncle, living chamber 

 or rate of growth. Nevertheless, we feel that we do not go amiss 

 when we refer one of the most common larger cephalopods of the 

 Chazy formation of New York to Hall's species, partly because there 

 is little danger of error, for no other equally large and equally closely 

 septate cephalopods occur in otir Chazy formation and partly be- 



