192 Prof. F. M'Coy on some new Lower Palaeozoic Mollusca. 



Murchisonia gyrogonia (M'Coy). 



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 strise, which, 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 



TUO' WIUIU y^(j. 



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. 

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

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

 ^pire. 



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 striae 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. 



