REPORT OF THE STATE PALEONTOLOGIST I903 



305 



and designated as endosiphocoleon. Holm termed the species at 

 the time, Endoceras gladius, but he later [1896, p.400] 

 reunited it with Endoceras (Nan no) belemniti- 

 forme. This again has been referred to Vaginoceras by Hyatt 

 [1895, p.9]. We will state on this occasion that while we had 

 worked out the characters of the endosiphuncular organs before 

 we w^ere aware of Holm's prior elaborate description, we found 

 by subsequent comparison that our material on the whole veri- 

 fies Holm's observations for the species in hand, but that at the 

 same time it indicates an origin of the endosiphotube and a rela- 

 tion between endosiphotube and endosiphocoleon which is dif- 

 ferent from those observed by Holm. These 

 and such other differences as have become ap- 

 parent between the endosiphuncular structures 

 of Vaginoceras belemnitiforme 

 and Cameroceras brainerdi will be 

 noted at the end of the description of these 

 structures in our species. We have copied 

 here for comparison Holm's figure of the 

 endosiphocoleon [text fig.4]. 



The endosiphocone which, at its forward 

 end, is subcircular and only slightly flattened 

 on the ventral (outer) side, becomes rapidly 

 flattened toward its posterior end, the convex 

 wall approaching the opposite flat one. It 

 thus runs out into a double blade, which, 



lying approximately in the middle of the siphuncle and parallel 

 to its flatter side, is at first almost as wide as the siphuncle 

 and nearly touches its walls [see pl.7, fig.i]. This is at least the 

 case in the large siphuncle of the later portions of the shell when 

 the animal approaches maturity. This organ is the endosiphocoleon, 

 which in our material consists just behind the endosiphocone of two 

 thin, intensely black conchiolinous walls, forming a flattened broad 

 tube. These walls are composed of extremely thin, concentric or 

 rather long conical lamellae. They show a double sculpture, viz, low 

 transverse ribs arching slightly forward and longitudinal lines 



Fig.4 Vaginoceras 

 belemnitiforme Holm 

 (sp."). Longitudinal section 

 of siphuncle,_showing endo- 

 siphocoleon " 

 Holm) 



(Copy from 



