FOSSILS OF THE NIAGARA GROUP. 399 



GENUS PORCELLIA (Leveille). 



SUBGENUS TEEMANOTUS (N. S.-G). 



Volutions apparently in the same plane ; umbilicus on both sides ; aper- 

 ture expanded : the dorsal line pierced by several oblong perforations. 



Tremanotus alpheus (n. s). 



Shell subdiscoid, making several volutions, which are rotund, wider than 

 deep, slightly embracing, rounded exteriorly, and very abruptly 

 curving into umbilicus. 



The specimen is a cast of the interior of the shell, and along the peri- 

 phery presents a range of elongated oval prominences which have appa- 

 rently been perforations in the shell, arranged at equal distances from 

 each other ; or they may have been flattened, hollow nodes which have 

 left these marks, and which originally communicated with the interior 

 of the shell. 



The surface has been marked by coarse longitudinal striae or ribs, the 

 traces of which are shown in the cast. 



This species bears some resemblance to Bucania angustata, but differs 

 in the more rotund volutions, and in the interrupted oblong nodes 

 representing the perforations on the periphery, while that species 

 is free from nodes or carina. From the subcarinate character of the 

 specimen figured as B. angustata in the Geology of Canada, page 334, I 

 am led to infer that it is rather identical with the species here described 

 than with the typical forms of the species to which it has been referred. 



Formation and Locality. — From the Niagara limestone of Illinois, Prof 

 C. U. Shepard. 



Among the collections from Wauwatosa, Waukesha, Racine and other 

 localities of the Niagara group, in Wisconsin, there are remains of 

 other species of Gasteropoda than those here described ; but their con- 

 dition is such that, for the most, their description or illustration would 

 add little to our positive knowledge of the subject. The description of 

 the interior casts of species of this class of fossils is usually even less 

 satisfactory than that of other fossils in a similar condition ; but as it 

 seems unlikely that we shall get them in any other form, we are compelled 

 to make such use of them as will aid in further comparisons of these 

 fossils with those from other localities. 



