FOSSILS OF TEE NIAGARA GROUP. 395 



A gutta percha cast shows the surface to be finely striated ; the flat- 

 tened space on the back of the volution is margined on each side by a 

 slender carina, and the striae between are apparently coarser than those 

 above or below. The height of the specimens varies from less than one 

 inch, to one inch and seven-eighths. The transverse diameter of the last 

 volution is about one inch. 



This species has a more elevated spire than T. unibilicata of the Tren- 

 ton limestone, and, so far as can be determined, has had no umbilicus. 



Formation and Locality. — In limestone of the Niagara group, at Racine 

 and Greenfield, Wisconsin. 



Tbochonema (Cyclonema'?) pauper, Hall. 



PLATE XV, FIGb. 5, G, 0; PLATE XXV, FIG. 13. 



Pleurotomaria pauper, Halt- ; in Twentieth Report N. Y. State Cabinet, 1st edit., p. 343. 1867. 



Shell small, obtusely conical, the apicial angle from seventy to eighty 

 degrees. Volutions three, four or more, rapidly increasing in size 

 from the apex, rounded above and on the sides, a little flattened on 

 the top below the suture line, the last one subangular below ; suture 

 distinct, not channelled. Aperture rounded or slightly elongated, 

 and scarcely subangular above on the inner side. Umbilical cavity 

 rather large, marked by three or four revolving bands. Surface 

 strongly striated ; the upper part of each volution marked by five 

 or six revolving cariniform strias above the stronger carina upon 

 the angle of the outer volution. These are crossed by fine lines of 

 growth, which are not always preserved in the fossil. 



Owing to the thickness of the shell, the internal casts do not often 

 preserve more than three or four bands indicating the exterior striae, and 

 the apicial angle is usually less than that of the exterior shell. 



This species has been identified by Prof Winchell as Pleurotomaria 

 halei ; and two specimens communicated by him under this name, are in 

 all respects identical with the species described by me under the name 

 Pleurotomaria paiqier, from which genus it must be separated on account 

 of the exterior character of the shell which has since been discovered. 



Formation and Locality. — In limestone of the age of the Niagara group, 

 at Racine, Wisconsin, and Bridgeport, Illinois. 



