BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 507 



•characters of the siphuncle and specially the extension and form of 

 the septal necks, in order to establish as far as possible the relation 

 ■of the species to the sub-orders distinguished by Hyatt. 



The specific characters of C . c o n f e r t i s s i m u m are briefly 

 the following : conch small, attaining a length of 40 mm ; curved thus 

 that an arc 20 mm long has a hight of 2.8 mm ; expanding gradually 

 at a rate of 1 :(i8) in the lateral direction and of 1 :ii in the dorso- 

 ventral direction. Section depressed elliptic, the two diameters at 

 the lower end of our specimen approximately in the ratio of 3 4, the 

 dorsal (inner side) flatter than the ventral one. 



Septa uniformly convex, depth one fourth the width. Sutures 

 straight transverse. Cameras shallow, 1 mm deep (10 septa within 

 the space of 10 mm). Extent of living chamber and aperture 

 imknown. 



Siphuncle very small, not more than one twelfth the minor diam- 

 eter of the conch, empty, situated propioventran, consisting of short* 

 septal necks and nearly tubular (very slightly contracted) siphun- 

 cular segments. 



Surface provided with bands of fine transverse lines. 



Position and localities. Fort Cassin beds at Fort Cassin Vt., 

 and Valcour N. Y. (A ri ). 



Observations. We have found it impossible to ascertain with the 

 material available the exact generic position of this form. As Whit- 

 field has rightly pointed out, this form is remarkable for its " trans- 

 versal form " (depressed section). This, combined with the closely 

 arranged septa and marginal, ventral position of the siphuncle. would 

 indicate that the form is not so primitive as the majority of its ortho- 

 ceraconic and cyrtoceraconic associates. The structure of the si- 

 phuncle would also seem to bear this out, for it is not only very 

 small and much reduced in size, but its septal necks are also short 

 and the greatest part of the siphuncular wall is formed by the siphun- 

 cular segments. The septal necks are, as far as we were able to 

 observe, straight and short and would indicate the position of the 

 form in question among the Orthochoanites. There has, however, 

 no genus been erected for orthochoanitic cyrtoceraconic forms with 

 such distinctly depressed section, as far as I am aware, and typically 

 depressed cyrtoceraconic conchs appear only among the much more 

 specialized genera of the order Cyrtochoanites. Whether our form 

 represents a primitive member of one of the latter will have to be 

 decided by future discoveries of the whole conch with living cham- 

 ber and aperture. 



