Description of Ten New Species of Fossils. 



80 



the other. The convex side of the tube hugs, closely, the interior of 

 the ventral side of the siphuncle, and, as it enlarges, the flattened side 

 approaches the dorsal side of the siphuncle until it well nigh fills the 

 internal area, as shown by the figures. It arises between the lines 

 that mark the septa, and, at this point, there is a slight expansion of 

 the siphuncle, marked by a convex swelling extending quite around 

 the siphuncle, but greatest upon the ventral side. 



It was collected by W. C. Egan, Esq., of Chicago, Illinois, in whose 

 honor I have proposed the specific name, in rocks of the age of the 

 Hudson River Group, at Bristol, in that State. 



Remarks. — The internal tubes of the Endoceras, as known to Prof. 

 Hall, at the time he founded the genus, were conical, and it seems, from 

 the " Observations on the purposes of the embryonic sheaths of Endo- 

 ceras, and their bearing on the origin of the siphon in the Orthocerata," 

 by R. P. Whitfield (Bull. No. 1, Am. Mus. Nat. Hist., 1881), that only 

 conical sheaths or tubes have, heretofore, been described in America. 

 In this species, it might be described as somewhat half conical, or 

 more nearly half wedge shaped. In the two specimens illustrated, the 

 siphuncles are crystalline, and the internal tubes are perfectly smooth 

 and without any indications of attachment to the surrounding siphun- 

 cle. If, therefore, the internal tube was constructed for the purpose 

 of the protection of the animal, after the apex of the shell had been 

 injured or worn away, we have a secondary tube constructed in a 

 wholl} r different form from the primary one; but, as it soon expands so 

 as to nearly fill the original siphuncle, the appearance, on the whole, 

 gives countenance to this view of its purpose, as advanced, by Prof. 

 Whitfield, in the paper above alluded to, if we except, possibly, the ex- 

 pansion of the siphuncle at the point of the commencement of the tube. 



Endoceras bristolense, n. sp. 



Plate IV., fig 2, showing the rapid expansion of the internal tube of the siphuncle; fig. 

 2d shows the marks of the septa on the siphuncle before the commencement of the internal 

 tube. 



This species is founded upon the siphuncle and the internal tube,'' 

 the external appearance of the outer shell being unknown. The si- 

 phuncle is rather rapidly tapering, at least, much more so than it is 

 in E. egani. The marks of the septa are moderately close together, 

 and cross the siphuncle diagonal^-, inclining toward the apex on the 

 ventral side, at an angle of about 40 degrees. The diameter of the 

 siphuncle, at the place at which the internal tube arises is about an 

 inch, and the septa are distant about 22 lOOths of an inch. 



