376 > NEW YORK STATE MUSEUI^I 



PLATE 9 



Cameroceras (Proterocameroceras) brainerdi Whitfield (sp.) 



1 Natural longitudinal section of fragment of siphuncle, showing in 



upper part fragment of outer surface of siphuncle with forward 

 curving of septa ; in middle part the white calcite layer of an 

 endosiphosheath, flanked on both sides by wings (w) and in 

 the lower part the endosiphocoleon (esco). x2 



2 Longitudinal section through a siphuncle, showing the endosipho- 



cone with its bounding endosiphosheath in the anterior part and 

 the endosiphocoleon (cut through the minor axis) forming in 

 the posterior part of the endosiphocone. There are also shown 

 farther apicad the bases of the other endosiphosheaths and in 

 the posterior transverse section the lateral end of the endosi- 

 phocoleon and an endosiphoblade, extending obliquely from the 

 same to the endosipholining. x2 

 Originals from the Beekmantowm formation at Valcour N. Y. 



Piloceras explanator Whitfield 



3 A transverse section through the posterior part of the siphuncle 



(the shaded part at the right hand side is obliquely cut for- 

 ward), showing the closely arranged endosiphosheaths; among 

 them the last (darker, innermost) endosiphosheath and an 

 endosiphofunicle (cut obliquely) extending at the left from the 

 lateral side of the endosiphocone. x2 

 Original from the Beekmantown formation at Valcour N. Y. 



