208 PALjEONTOLOGY of NEW-YORK. 



siphuncle, more approximate than the annulations ; siphuncle large, subdorsal, containing 

 a smooth emljryo tube ; section circular. 



A fragment of tliis species, two feet in length, is all that I have seen, thougli the original 

 must have been at least three times this length. This is the largest of the annulated species, 

 and is clearly different from all the others in the rock, which have small siphons, and are 

 of far smaller size, with more abruptly elevated annulations. The annulations in this species 

 are broadly arched on the dorsal side, which is at the left hand of fig. 1 a. The septa are 

 direct and plainly arched, being distant about three fourths as far as the annulations. The 

 internal tube, within the siphon, is not annulated. There is also, apparently, the apex of 

 another tube within this one, which is not central ; but this appearance may be due to 

 accidental displacement. 



Fig. 1 a. Lateral view of a fragment, showing- the arching of the annulations towards the left side. 



The fine dark transverse lines indicate the edges of the septa. 

 Fig. 1 b. Longitudinal section of the last, showing the position of the siphuncle, convexity of the septa, 



and internal tubes. 



Position and locality. This species occurs in the compact lower strata of the Trenton 

 limestone at Watertown. (Frvm Dr. Crawe.) 



ENDOCERAS PROTEIFORME {n. sp.) 



Plates XLV. to L., & LIII. 



General form cylindrico-conical, more or less elongated, often compressed, tapering 

 somewhat unequally in different specimens ; young specimens terminating in an extremely 

 acute point ; surface marked by distinct transverse stria, which usually appear like narrow 

 subimbricating bands, with one edge well defined and more elevated than the other, more 

 or less distinctly striated longitudinally ; stri^ varying from extreme tenuity to distinct 

 elevated threadlike lines ; section circular ; septa distant from one fifth to one fourth the 

 diameter ; siphuncle excentric or submarginal.* 



I ara able to characterize three distinct varieties of this species, which are the prevailing 

 forms : these depend mainly on the surface markings of the young shell. The old shells are 

 recognized by a large submarginal siphuncle, which usually contains a smooth cylindrico- 

 conical embryo tube or sheath. This tube is sometimes irregularly tapering, and always 

 free from visible ,'urface markings or sculpture. Within this embryo tube are the young 

 shells, sometimes perfectly formed Orthocerata, and at other times destitute of septa or 



* This is a very variable species, wliich, in its extreme varieties, I have been disposed to regard as specifically 

 distinct. TiiG engravings of the two first plates (xlv and xlvi) were made with this view; and the parent shell, with 

 the smooth embryo tubes figured on the subsequent plates, was considered distinct, presenting no characters which 

 could be identified as common with those figured on Plate xlv. It is only by some fortunate discoveries made since the 

 engraving was comijleted, and while my descriptions are passing through the press, that I_am able to present the tnie 

 characters of this protean species. The two plates xlv and xlvi were figured during the early part of the jireparation 

 of this work in 1843, and my subse(]ucnt investigations have furnished the other specimens which appear on the 

 following plates. This will account for the want of unity or completeness in the grouping of the different varieties. 



