yj2 NEW YORK STATE MUSEUM 



PLATE 7 



Cameroceras (Proterocameroceras) brainerdi Whitfield (sp.) 



1 Natural longitudinal section of part of siphuncle, showing the 



broad black conchiolinous endosiphocoleon at the upper end 

 (esco) and the sections of the wings (w), separated by the 

 endosiphosheaths. At the lower end a posterior trans- 

 verse section of the fragment, with broad flat endosiphoco- 

 leon (esco) and the embracing wings (w) is figured. x2 



2 Further enlargement of the endosiphocoleon of figure i (x4), 



to show the central thickening of the endosiphocoleon which 

 leads to the formation of the endosiphotube 

 3-10 A series of transverse sections (except figure 4) through the 

 farther posterior continuation of the fragment reproduced 

 in figure i. All x2 



3 Shows, like all the farther sections, the endosipholining, the 



central endosiphocoleon, one complete pair and half of a 

 second one, of crescent-shaped sections of wings 



4 Upper figure, longitudinal section of a block (x2) to show 



a sudden turn of the endosiphocoleon and lower figure, 

 transverse section of farther end of the same block 



5 Shows the endosiphotube inclosed within the endosiphocoleon 



which has been reduced to a double plate 



The folk)wing figures 6-10 illustrate the apicad reduction of 

 the diameter of the endosiphotube and the gradual disappear- 

 ance of the endosiphocoleon (the lithographer has shaded 

 this organ too dark in figures 9 and 10, and notably so the 

 lower half in figure 10, as well as the interspaces between 

 the endosipholining and the endosiphocoleon). The appar- 

 ent wabbling of the endosiphocoleon from the left to the 

 right side in these sections is due to the fact that some are 

 drawn from the anterior and others from the posterior ends 

 of blocks. 



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



