CEPHALOPODA. T715 
Cameroceras, | 
Genus CAMEROCERAS, Conrad, 1839. 
Endoceras, HALL, 1847. 
The collection is fairly abundant in specimens referable to this genus. Few, 
however, are sufficiently complete to justify the determination of their specific 
characters, though the evidence afforded by them indicates the probable presence of 
several species. Of more interest than the variation in specific features is the 
interesting illustration of the structure of the sipho which is represented by many 
and various forms of internal casts of the organ. With all that has been written 
upon the relation of the sipho of this genus to the septa and conch, there still remains 
much to be learned in regard to the structure of Cameroceras, and some light is 
thrown upon obscure points by these specimens. We have here adopted without 
reserve Conrad’s term Cameroceras in place of the more generally accepted name 
Endoceras. Whitfield has employed the former term with a suggestion that there 
may prove to be a generic difference in the two structures, but this seems to us, 
with the present evidence, scarcely possible. The distinction which has been 
recognized between the two by Hyatt is that in Hndoceras the siphon is not lined by 
a continuous shell layer but is composed of a succession of septal funnels, overlapping 
at their edges, while in Cameroceras (which this author regards as a synonym of 
Sannionites, Fischer de Waldheim, 1837), the siphon is a continuous layer. The 
typical species of Endoceras (E. proteiforme Hall) is vastly better known than that 
of Cameroceras (C. trentonense), and while it has been impossible for me to carry out 
a generic distinction in the two, the fact must be recognized that the latter term 
was introduced in 1839 and the former not until 1847. Conrad, also, in 1839 employed 
the name Diploceras (D. vanuxemi, type) for a shell from Trenton Falls, N. Y., which 
is unquestionably a Cameroceras, and the species probably the same as Endo- 
 ceras proteiforme. Hall*, Whitfield}, Dewitz{, Holm§, Foord| and others have shown 
the existence of a continuous sheath situated at, and composing the apical portion 
of the sipho, often thick-walled, and extremely so about the apex itself. These have 
been sometimes termed “embryo-tubes” and also “siphonal sheaths,” as though 
they existed within the sipho and were not an integral part of the sipho itself. 
Such bodies, of which internal casts abound in the Trenton formation of Minnesota, 
are the thickened extremital portions of siphones; the septa lie against them (or at 
least, aguinst their upper portions) in a normal position, and above its free 
edges the sipho is a discontinuous sheath composed of the overlapping and 
+ Bull. Amer. Mus. Nat. Hist., vol. i, no. 1, pp. 20—28. 1881. 
* Paleontology of New York, vol. i, pp. 208 et. seq.. pls. 48—50, 53, etc. 1847. 
+ Zeitschr. der deutsch. geol. Geselisch., vol. xxxii, pp. 371—393, pls 16, 17. 1860. 
§ Dames and Kayser’s Paliontologische Abhandlungen, Bnd. iii, Heft1. 1885. 
| Ann, and Mag. Nat. Hist., Dec., 1887, pp. 393—402, 
