136 



Length of specimen figured, i6 mm.; breadth of body whorl, 

 3 mm. Other shells from Penton would be 'larger if perfect. 

 The specimens from Mosedale are much smaller; the largest I 

 have found, if perfect, would only be about 6 mm. in length. 



Locality and Horizon. — This shell is tolerably abundant in the 

 Calciferous Sandstone Series at Penton. 1 have collected more 

 than sixty specimens there, in different stages of growth. Mr. 

 Young has specimens in his collection from the shales of the Lower 

 Limestone Series of Craigenglen. They are about the same size 

 as those from Penton, and the lines of growth are preserved on 

 many of them. He has also small shells from the shales of the 

 Upper Limestone Series of Robroyston. I have also portions of 

 several shells from the Yoredale Shales near Askrigg, Wensley 

 Dale, which are of nearly the same dimensions as those from 

 Penton. Small casts occur in the Yoredale Rocks at Mosedale, 

 on the north slopes of Widdle Fell. 



