102 Prof. F. M^Coy on some new Lower Palceozoic Mollusca, 



Murchisonia gyrogonia {M^Qoy). 



Desc. Acutely conical ; apical angle 45° ; spire of three and a half 

 whorlsj very strongly angulated in the middle by the pro- 

 jection of an acute carina^ the upper and under sides of the 

 volution being flat and steeply inclined ; sutural angle 70° to 

 75°; body- whorl rounded below, with an additional fine keel 

 about halfway between the principal one and the anterior end, 

 which is almost hid by the suture on the spiral whorls ; sur- 

 face (when preserved) marked with sharp striae, w^hich, on the 

 upper part of the whorl, extend from the suture obliquely 

 backwards to the keel, curving in the opposite direction below 

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



5 5 Tvirli-Ti 7 



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 ; 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 



