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NEW YORK STATE MUSEUM 



form, as in N a n n o a u 1 e m a (according to Hyatt's observations) 

 the endosiphuncle communicated for a time with the exterior, viz 

 from the time of the destruction of the protoconch to that of the 

 plugging of the canal between the first and second endocones. At 

 the time of the burial of the shell in mud, this short end of the canal 



was still open and the surrounding 

 mud could enter it. In the remaining 

 portion of the endosiphuncle there 

 has nowhere been found any matrix,, 

 in our material, not even directly 

 behind the Spiess, which is always- 

 filled to near its tip with mud. Holm 

 comments on this fact, but states that 

 longitudinal sections through the endo- 

 siphuncle nowhere suggested the pres- 

 ence of any transverse partitions and 

 assumes that soft parts of the decaying 

 animal, remaining in the " Spiess "" 

 prevented the mud from entering the 

 endosiphuncle, which apparently was 

 through the lifetime of the animal in 



In 



Nanno aulema however, as men- 

 tioned above, Hyatt observed a closing of the tube in front of the 

 first endocone. Partition lines, forming acute angles with the endo- 

 siphon, leave no doubt that also the apical cone of Cameroceras 

 b r a i n e r d i was provided with endocones though no traces of 

 the same have been observed close to the apex. 



iWhiteaves [Roy. Soc. Can. Proc. & Trans. 1891, 9:79] has recorded 

 that in one specimen of Endoceras (E. crassisiphonatum) 

 from the Trenton limestone of Manitoba, " the interior of the narrow 

 posterior end of the siphuncle (endosiphuncle) appears to be portioned 

 off by a few transverse concave dissepiments" [see text fig. ij. Since 

 there exists an early genns (Diphragmoceras Hyatt) in which the 

 siphuncle is divided by tabulae alternating with the septa of the 

 camerated shell, it is quite as possible that the endosiphuncle also may 

 have been tabulated in some forms, though Whiteaves's observation 

 seems to stand quite alone at the present time. The observations of 

 both Hyatt and Whiteaves would seem to support Zittel's view that 

 the siphuncle has no particular function but is only a residual. 



Fig. I Endoceras crassisipho- 

 natum Whiteaves. Shows apparent 



fr^m'ro^elvi") ^'''^°''^^""''^^" ^^""^^ "P^^^ Connection with the latter.^ 



