86 



Cincinnati Society of Natural History. 



The internal tube arises centrally or subcentrally, and veiy rapidly 

 expands in a conical shape, until it fills, or nearly fills, the interior 

 space of the siphuncle. The specimens examined are crystalline, and 

 the internal tubes are perfectly smooth, without any indications of at- 

 tachment to the surrounding siphuncle, in the upper part; but from 

 the rapid expansion, and the nearness to the shell of the siphuncle, at 

 the points observed, we ma}' fairly infer that it unites with the si- 

 phuncle, at no great anterior distance, thus forming a protection to 

 the animal from injuries to the apex of the shell, or cutting off its 

 means of attachment or its habitation from the older part of the shell, 

 when it was no longer needed or desired. 



It was collected by W. C. Egan, Esq., in rocks of the age of the 

 Hudson River Group, at Bristol, Illinois. 



*Endoceras in^equabile, n. sp. 



Plate IV., fig. 3 and 3a, natural size. 



This species is founded upon the siphuncle, all other parts being- 

 unknown. The siphuncle is straight upon one side. It commences 

 at a point and somewhat rapidly swells upon one side for the distance 

 of about an inch, and then slowly contracts itself upon that side until 

 it forms a true cylinder, forward of which, as far as our specimen is 

 preserved, which is more than an inch, there is neither expansion nor 

 contraction. The marks of the septa, upon the cylindrical part, are 

 distant about half the diameter of the siphuncle, cross it diagonal^-, 

 and inclining forward, upon the straight side, at an angle of about 30 

 degrees. If we judge b}' the inclination of the septa, in comparison 

 with other species, the straight side will be the dorsal, and the dis- 

 tended side, the ventral. Having three specimens of this peculiar si- 

 phuncle, I have no doubt that it is a normal form aud represents a 

 particular species, though it would have been more gratifying, if the 

 specimens had shown other characters in addition to those defined. 



It was collected by W. C. Egan, of Chicago, in rocks of the age of 

 the Hudson River Group, at Bristol, Illinois. These three species of 

 Endoceras present characters so distinct from any known to the au- 

 thor, from rocks of the same age in thi& vicing, that they have been 

 to him of special interest. 



CANCELLARIA LIVINGSTONENS1S. n. Sp. 



Plate IV, fig. 4, an aperture view ; 4a, dorsal view, both very poorly executed, but bear- 

 ing such resemblance as to be of some service in identification. 



Shell obliquely subovate, spire depressed, and rising but little above 



