3/0 NEW YORK STATE MUSEUM 



PLATE 6 



Cameroceras (Proterocameroceras) brainerdi AMiitfield (sp.) 



1 Natural section of fragment showing the passage of the siphuncle 



into the Hying chamber and the absence of the endosiphohning 



in the anterior part of the siphuncle (endosiphocylinder). 

 Xatural size 



2 Xatural (slightly oblique) section through posterior part of livings 



chamber and anterior part of the endosiphocylinder, showing 

 the structure of tlie ectosiphuncle (length of septal necks and 

 absence of endosiphohning). Xatural size 



3 X^atural 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 tlie apical end, the endosipholining,. 

 the endosiphotube and some of the endosiphosheaths. X^aturat 

 size 

 Originals from the Beekmantown limestone at A'alcour X. Y. 



