﻿M2 



Cincinnati Society of Natural History. 



feature is the bladder-like expansion of the siphuncle. It was described 

 originally from the Trenton of New York. It has been found at Nash- 

 ville and occasionally here. 



Genusz- dOLPOCERAS, Hall. 1850. 



Third Annual Report, Reg. Univ. of N. Y. p. 181. 



" Cylindrical or sub-cylindrical, septa oblique to the axis of the shell, 

 regularly arched on the dorsal side, and bending downward in a deep 

 sinus towards the mouth on the ventral side." 



I. C. ARCUATUM, n. Sp. 



Arcuata from Lat Areuatus, arched, from the arched septa. 

 (Plate IY. figs. 1 a 1 b.) 



Shell medium size, moderately tapering; septa wide, to x / 2 inch, 

 with a slightly elevated suture between each ; strongly and regularly arched 

 upward on dorsal side, and as strongly and regularly curved downward on 

 the ventral, so that from two aspects the septa have an oblique direction ; 

 there is no acute angle to the septa as described in C. elarkana, Weth., 

 nor a deep sinus as noted in C. virgatum, Hall; surface irregular, often 

 encrusted with fragments of crinoid stems or some species of corah si- 

 phuncle apparently none, as the whole interior of the shell seems to be 

 filled with a finely comminuted mass of fossil particles. 



Locality : Cincinnati. 



The type is in the collection of this society. Mr. U. P. James has 

 specimens of the same species. 



This species differs from both those heretofore described in having the 

 septa regularly curved and arched. The type specimen, 6)4 inches long, 

 has fifteen chambers and is compressed at the larger end. Its diameter at 

 the small end is about of an inch and at the larger 1^ inches. A well 

 marked ridge runs along one side, which may have been caused by com- 

 pression. Another specimen, however, has a similar ridge, is five inches 

 long and has twelve chambers. It is also compressed at the larger end. 



Genus 3. ENDOCERAS, Hall. 1847. 



Pal. of N. Y. I, pp. 58 and 207. 



Siphuncle large, lateral or eccentric, marked or ridged on the outer 

 surface by the septa, which from their oblique direction give it the appear- 

 ance of a tube with spiral lines ; siphuncle enclosing from one to five 

 elongated conical tubes. 



