588 



NEW YORK STATE MUSEUM 



Plectoceras jason Billings (sp.) 



Page 484 

 See pi. 29 ; 31 



I Exterior view of a gerontic living chamber with very distant 

 costae 



The original is from the lower Chazy limestone (B 4 of the section 

 on page 398) at the Valcour shore and now in the New York 

 State Museum. 



