370 NEW YORK STATE MUSEUM 



PLATE 6 



Cameroceras (Proterocameroceras) brainerdi Whitfield (sp,) 



1 Natural section of fragment showing the passage of the siphuncle 



into the living chamber and the absence of the endosipholining 

 in the anterior part of the siphuncle (endosiphocylinder). 

 Natural size 



2 Natural (slightly oblique) section through posterior part of living 



chamber and anterior part of the endosiphocylinder, showing 

 the structure of the ectosiphuncle (length of septal necks and 

 absence of endosipholining). Natural size 



3 Natural section of nepionic bulb and posterior part of phragmo- 



cone, showing the length and form of the nepionic bulb, the 

 slight constriction at the beginning of the phragmocone (where 

 on the right side the first four small septa are left out in the 

 drawing) ; the cicatrix at the apical end, the endosipholining, 

 the endosiphotube and some of the endosiphosheaths. Natural 

 size 

 Originals froni the Beekmantown limestone at Valcour N. Y. 



