GENUS PLEUROTOMARIA. 343 



same species. In a specimen of the same size as the figure cited, the middle 

 of the last volution is subcarinate and flattened above. The spire is a little 

 more elevated than the figure, and the last volution a little more ventricose 

 below. It may prove to be a distinct species. Another specimen of similar 

 form does not possess the flattened band, while the lower side of the last 

 volution is flattened. 



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

 Wisconsin. 



HOLOPEA GUELPHENSIS. 



Holopea guelphensis : Billings, New Species of Silurian Fossils, p. 159, f. 143. 1862. 



Several fragments of a species, differing from any other in the collection, 

 resemble the Canadian species ; but being all quite imperfect, no full com- 

 parisons can be made. 



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

 Wisconsin. 



GENUS PLEUROTOMARIA (De France). 



PLEUROTOMARIA PAUPER (n. s.) ^ '^ K^ Aa^ At^^i 



Shell small, depressed conical, the apicial angle being about 70 or 75 

 deg. ; volutions three or four, rounded and somewhat rapidly increasing 

 in size from the apex : the aperture has been a little longer than wide. 

 The specimens occur in the condition of casts, which preserve the evi- 

 dence of a spiral band a little above the middle of the volution, and 

 between this and the suture line there is a slightly elevated line or slender 

 carina. 



The surface of the shell is unknown. 



Formation and locality. In the limestone of the Niagara group, at 

 Racine, Wisconsin. 



PLEUROTOMARIA LABROSA, var. OCCIDENS. ?, ©f^ 



Pleurotomaria labrosa : Hall, Pal. N. Y. Yol. iii, pa. 339, pi. 66. 



Shell somewhat rhomboidal-ovate : spire moderately elevated ; volutions 

 about three, the last one rapidly expanding, subangular, and marked 

 by a spiral band a little above the middle : upper side somewhat flattened ; 

 lower side rounded, and in the last one becoming ventricose. 



Surface marked by strong revolving and transverse striae. 



This species resembles in all important features the P. labrosa from the 



Lower Helderberg group. The specimens from Wisconsin are all smaller 



than those from New- York, and, in this respect only, show any constant 



differences. 



39 



