586 



NEW YORK STATE MUSEUM 



Plectoceras jason Billings (sp.) 



Page 484 



See pi. 30; 31 



I Exterior view of a large specimen, exhibiting the rate of growth 

 and 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. 



