EXPLANATION OF THE PLATES. 387 



Fig. 



8. Scalpellum villosiim, magnified one and a half the 



natural size. 

 8a, b. „ „ (a.) Internal view of rostrum. 



(b.) ,, „ sub-rostrum. 



TAB. VII. 



1. Pollicipes cornucopia, (one and a half nat. size.) 

 la. „ ,, internal view of valves. 



2. Pollicipes polj/merus, (one and a half nat. size.) 

 2a. ,, ,. internal view of valves. 



3. Pollicipes mitella, nat. size. 



3# '. „ „ nat. size, internal views of 



(a.) Scutum, and of 

 (6.) Tergum, showing articular fold. 

 ZU . „ ,, Internal view of other valves, in a 



small specimen, showing the manner in which 

 the valves of the lower whorl overlap each other. 

 (a.) Upper latera. 

 (b.) Carina, 



(c.) Sub-carina, both viewed a little obliquely. 

 (d.) Rostrum, 

 (e.) Sub-rostrum, both viewed a little obliquely. 



4. Pollicipes spinosus, one and a half nat. size. 



5. Pollicipes sertus, one and a half nat size. 



TAB. VIII. 



1. A piece of rock bored in two directions by Litho- 

 trya dorsalis, with the calcareous basal discs in 

 the upper cavity, serving as a bridge for crossing 

 an old cavity. About twice natural size. 



