244 



PALEOZOIC MOLLUSCA. 



backwards to the keel, curving in the opposite direction below 

 the keel. Length 4^ lines, proportional length of last whorl 

 xVn. width T?A. 



This is most allied to the Murchisonia perangulata (Hall) of 

 the Bird's-eye limestone of the New York series, but is distin- 

 guished by the shortness of the spire in proportion to the body- 

 whorl, and by the additional keel below the band on the last 

 turn. It is also closely allied to the M. pulchra (M'Coy, Sil. 

 Foss. Irel. t. 1. fig. 19), but is on comparison found to be di- 

 stinct by the fewer, longer, and more produced whorls of the 

 spire. 



Very abundant in the fine sandy schists of Ysputty Evan, 

 N. Wales; also in the calcareous strata W. of Llanfechan, Mont- 

 gomeryshire. 



(Col. University of Cambridge.) 



Murchisonia simplex (M'Coy). 



Desc. Acutely conical ; apical angle 55° ; spire of about four or 

 five whorls, angulated in the middle by the projection of an 

 obtuse thick keel, another keel a little smaller between the 

 suture and the keel above, and a third nearer the suture be- 

 low on each turn ; surface marked with fine strise of growth, 

 arched back to the keel at a moderate angle above, and nearly 

 vertical below j base imperforate. Width of small specimens 

 6 lines, length of last turn 5 lines (imperfect specimens double 

 this size). 



The more elongate form and imperforate base distinguish this 

 species from some of the " Trenton limestone " varieties of the 

 Pleurotomaria umbilicata (Hall) ; and the same characters and 

 the absence of the spiral strise on the base distinguish it from the 

 Euomphalus triporcatus (M'Coy). 



I should have supposed the M. scalaris (Sow. and Salt.), Geol. 

 Journ. vol. v. t. 1 . fig. 2, Ayrshire, belonged to this species, but 

 that one, instead of five, keels are indicated in the figure and 

 text. 



Limestone of Allt yr Anker, Meifod, Montgomeryshire; also 

 in the sandstone of Dalquorhan, near Girvan, Ayrshire ; greenish 

 trappean sandstone of Glenquhaple, Ayrshire. 



[Col. University of Cambridge.) 



Murchisonia torquata (M'Coy). 



Desc. Acutely conic ;> apical angle about 26° ; whorls six, having 

 a thickened prominent suture, below which the upper portion 



I 



