dOB PALiEONTOLOOY OF NEW-YORK. 



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

 a smooth embryo tube ; section circular. 



A fragment of this species, two feet in length, is all that I have seen, though 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. 

 Pig. 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. (From Dr. Cbawb.) 



ENDOCERAS PROTEIFORME {n. sp.) 

 P1.ATE8 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 striae, which usually appear like narrow 

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

 or less distinctly striated longitudinally ; striae 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 am 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 surface markings or sculpture. Within this embryo tube are the young 

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



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

 distinct Tae 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 completed, and while my descriptions are passing through the press, that I,am able to present the true 

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

 of this work in 1843, and my subsequent 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. 



