374 • ^'J^'^^' YORK STATE MUSEUM 



PLATE 8 



Cameroceras (Proterocameroceras) brainerdi Whitfield (sp.) 



1 Natural longitudinal section of part of siphuncle of young" speci- 



men, showing matrix filling, smooth endosiphocone and con- 

 tinuation of the latter with the endosiphocoleon cut through its 

 minor axis. Natural size 



2 Longitudinal section of fragment of siphuncle, showing uninter- 



rupted continuation of endosiphocoleon (cut through its minor 

 axis) and an endosiphosheath. The upper transverse section 

 shows half of the endosiphocoleon and two wings. Natural size 



3 Natural longitudinal section of fragment of young siphuncle, 



retaining the matrix filling of the endosiphocone, which shows 

 an undulating outline. Natural size 



4 Transverse section of young siphuncle, showing the endosipho- 



blades and endosiphotubes. x2 



5 Transverse section of siphuncle, showing endosiphotube, three 



endosiphoblades and endosipholining. x3 



6 Transverse section at jXDSterior end of fragment reproduced by 



figure 3, showing young endosiphocoleon and three endosipho- 

 blades. Natural size 



7 Natural transverse section of sliell, showing the siphuncle with 



the section of the endosiphocone (in the center) and the three 

 calcareous endosiphoblades fastening it to the ectosiphuncle 

 (two situated laterally and one below) leaving cavities between 

 them, which are filled with matrix. For comparison with 

 figures 5 and 6 the figure should be inverted. x2 



8 A section of the sam.e specimen, situated farther apicad and show- 



ing the endosiphotube and rapid disappearance of the endosi- 

 phocoleon. These parts are less distinct in the specimen than in 

 the drawing. x2 

 Originals are from the Beekmantown limestone at Valcour 

 N. Y. 



