GENUS PORCELLIA. . 347 



GENUS PORCELLIA (Leveille). 



SUBGENUS TREMANOTUS ( n. s.). 



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 the 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.* 



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^ cited above, 

 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 Greology 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. 



CEPHALOPODA. 



GENUS PHRAGMOCERAS (Broderip). 

 PHRAGMOCERAS NESTOR ( n. s.). 



A fragment preserving the outer chamber and several of the septa, is 

 ventricose, broadly expanded in the dorso-ventral direction, and measuring 

 from the extreme limits of the apertures, which are marginal, more than 

 two and a half inches ; the length of the narrow constriction between them 

 being one inch and a quarter. Both the dorsal and ventral apertures are 

 marginal and expanded. 



* The only other explanation that can be given to these markings is that they are 

 flattened, hollow nodes which have left these marks, and which originally\ommuni- 

 cated with the interior of the shell. 



