4l8 NEW YORK STATE MUSEUM 



entire phragmocone filled solidly. It must have been impossible 

 for the latter to move to greater distances and they must have lived 

 much as the recent octopus which prefers to sit in cavities of the 

 rocky bottom, and thence to extend its arms in all directions in 

 search of prey. 



The complete filling of the cameras of some individuals and the 

 absence of the deposition in others is at variance with the view that 

 the deposit served to counteract the buoyancy of the air supposed 

 to have been in the air chambers^ and to give strength to the shell. 

 Nor can we see how these heavy unwieldy shells could have been 

 carried in a vertical position without making the animal top-heavy. 

 On the other hand it is readily understood what advantage this solid 

 block of lime that could be driven into the ground like a post, would 

 have offered to the animal in turbulent water. 



From the similar Cameroceras tenuiseptum Hall, this 

 species is distinguished by the greater depth of the chambers and 

 the smaller size of the siphuncle. 



Genus endoceras (Hall) emend. Hyatt 

 Endoceras (?) champlainense sp. no v. 



Plate T, figure 1-4 



In the Beekmantown beds D at Beekmantown I have collected 

 several orthoceracones and siphuncles, which were at first thought 

 to belong to O . p r i m i g e n i u m , the only species of Orthoceras 

 thus far described from the Beekmantown formation of New York. 

 Subsequent study and comparison with the types of that species have 

 shown that the present form is readily distinguishable from the long 

 known O . p r i m i g e n i u m by its deeper chambers and larger 

 siphuncle. 



Description. Conch of rather small size, straight, very gradu- 

 ally expanding, at the rate of about i mm in 15 mm. The apertural 

 diameter of the largest specimen observed about 25 mm ; and the 

 corresponding length of the conch about 275 mm ; the latter esti- 

 mate being somewhat conjectural and based upon the rate of expan- 

 sion. Cross-section elliptic ( ?) ; minor and major diameters in liv- 

 ing chambers 14 mm and 24 mm respectively, but conch probably 

 slightly compressed. The surface apparently smooth, and in the 

 ephebic stage provided Avith transverse lines only. 



1 The writer has in the paper cited, adduced evidence for the conten- 

 tion that the cameras became filled with gas only after the death of th^ 

 animal or when it was brought to the surface of the water. 



