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NEW YORK STATE MUSEUM 



That in the species of Cameroceras, as in C . brainerdi, the 

 siphuncles are met with so frequently where the phragmocone has 

 been destroyed, is not to be wondered at as they have become filled 

 with organic deposits of carbonate of lime ; but in Endoceras 

 champlainense, as an example, we also find the empty portions 

 of the siphuncles more frequently than the phragmocones. This is 

 due to the relatively stouter walls of the siphuncles of these earlier 

 species and to the fact that in them the siphuncular necks or fun- 

 nels reach still from each septum to the preceding one, thus forming 

 a completely closed and stout tube, while in later forms these necks 

 become reduced and only secondary, frequently but membranous 

 annuli or siphuncular segments complete the tube. The larger size 

 and more complete sheathing of the siphuncles of the earlier ortho- 

 ceracones leave no doubt of the greater importance of the siphuncle 

 or of its contents to the animal in Lower Siluric time, than at any 

 later period. These siphuncular chambers were doubtless occupied 

 by an extension of the mantle and where they have such relatively 

 large dimensions as in Cameroceras brainerdi they con- 

 tained undoubtedly also portions of the viscera. Whatever the origi- 

 nal function of the fleshy siphuncle may have been, if it had any, it 

 was clearly in a retrograde condition, and Zittel's suggestion [Hand- 

 buch, p. 349 1 that it had no physiologic function but was merely a 

 remnant to be explained by the evolutionary history of the animal, 

 appears to be quite acceptable. 



E . (?) champlainense would, by its appearance, be readily 

 taken for an Orthoceras and we had to compare it with several 

 Canadian species of Orthoceras, thereby using the latter term in its 

 old sense ; but it is evident that this species like probably nearly all of 

 the earlier species which have been referred to Orthoceras, can not 

 belong to the genus in the restricted scope given to it by Hyatt, 

 or even to the Orthoceratidae, 3 for the reason that the mode of 

 preservation of the siphuncles indicates that the septal neck extended 

 always from one septum at least to the next preceding. This, how- 

 ever, is the diagnostic character of Hyatt's suborder Holochoanites, 

 while in the later Orthochoanites to which the Orthoceratidae be- 

 long, the funnels have become short and reduced and the siphuncle 



1 Hyatt's more precise and detailed delimitation of the genera of the 

 earlier orthoceracones invites an investigation of the numerous species 

 of Orthoceras described from the Lower Siluric in regard to their generic 

 relations. Orthoceras primigenium for instance is, as, the pre- 

 vailing preservation of its solid apical cone indicates, not a true Orthoceras 

 [see p. 505!- 



