198 SILURIAN MOLLUSCA. 



agrees with the P. sublavis (M'Coy) of the Irish Silurian rocks, 

 but from which it is distinguished by its fine close striation. 



Common in the Upper Ludlow shale of Cwm Craig Ddu ; Mid- 

 dleton Park near Sedburgh ; Erw Gillfach, and in the Ludlow 

 schists above Parklane; Upper Ludlow rock of Benson Knot^ 

 Kendal, Westmoreland ; also in the sandy schists of Pont-ar-y- 

 llechan. 



[Col. University of Cambridge.) 



