EEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 505 



portion of the phragmocone, which he refers to Vanuxem's species. 

 From this material he extracted the following description : 



Elongated, terete, gradually tapering to an obtuse point ; surface 

 smooth ?, section circular, septa thin, deeply concave, closely ap- 

 proximated, being distant only one twenty-fifth the diameter; 

 siphuncle ?. 



It is stated that this species is found in the higher calcareous por- 

 tion of the Calciferous (Beekmantown) formation in the Mohawk 

 valley^ near Fort Plain, and that it occurs also in a brecciated mass 

 near the same place. 



Prof. Whitfield has assigned to this species a specimen, consist- 

 ing of a longitudinal section, which had been obtained by Professor 

 Seely at Beekmantown. He concedes that the septa in the 

 same are not so closely arranged as in Hall's type, nor are they so 

 deeply concave, but adds that it agrees with a fragment of Ortho- 

 ceras which lies on the same block with Hall's type of Maclurea 

 m a t u t i n a from the Mohawk valley. His material, like that of 

 the preceding observers, failed to show either the extent of the 

 living chamber or the character of the siphuncle. 



Prof. Cleland only states the presence of a few imperfect speci- 

 mens in the Fort Hunter section. 



While the specimen compared by Whitfield with Hall's original of 

 O . p r i m i g e n i u m differs from the latter by its deeper cham- 

 bers, it agrees well in this character with the original figure given 

 by Vanuxem. It is probable that Hall's figure [/. c, fig. 11] repre- 

 sents a species different from that which Vanuxem had in hand. If, 

 however, the siphuncle of Whitfield's original has indeed been small 

 and subcentral, as is suggested by that author, then his O . p r i m i - 

 g e n i u m is quite surely a different form, for the O . p r i m i - 

 g e n i u m of the Mohawk occurs prevailingly and in great numbers 

 in the form of the solid apical ends which are evidently the preseptal 

 or nepionic bulbs and indicate a species with a wide siphuncle, 

 such as a Cameroceras or Endoceras had. 



These considerations invite a preliminary separation of the forms 

 from Beekmantown and from the Mohawk valley as a safer pro- 

 cedure until more complete material of both the former and latter 

 has been secured. The species from the Champlain valley is prob- 

 ably nearer related to O. deparcum Billings from the White 

 limestone (Beekmantown) of the Mingan islands. 



From the associated form here described as Endoceras ? 

 champlainense, it dift'ers in its more closely arranged septa, 

 greater rate of growth and perhaps also in the position of the 

 siphuncle. 



