226 



OUR COMMON BRITISH FOSSILS. 



latter — and by them this group of fossils were called 

 Lampades, 



The structure of the shells of Brachiopoda (as 





Fig. 



-Cranue, showing exterior and Interior of shells. 



Dr. Carpenter has clearly shown) is different from 

 that of the bivalves or Lamellibranchiate mollusca, 



Fig. jgg.—Siro/homena de^ressa, showing exterior and interior of valves (Silurian). 



although it represents one stage in the formation of 

 the shells of the latter — that of the outer layer. 



Fig. 200. — Strophomena 

 rug-osa. 



Fig. 20I. — Rhynchonella pugniis 

 (Carboniferous limestone). 



Owing to the large size of the " arms " (as they are 

 still technically called) of most of the Brachiopods, 

 the interior of the valves contain remarkable struc- 



