FOSSIL LAMP.SHELLS. 237 



individuals. The most notable form in the Devonian 

 rocks is Calceola, which occurs in such numbers near 

 Torquay and Newton that the rocks are technically 

 called " Calceola-beds." Every geological formation, 



Fig. 22i.—Terel)rahila, one valve showing large internal loop. 



and most subdivisions, have their suite of peculiar 

 Brachiopods. The coins of the later Roman empire 

 do not succeed each other more rapidly than do these 



Fig. 223. — Terehratula 



caj>ut-serpentis (recent, 



but supposed to be 



Fig. 222. —Recent species identical with 7". j^r/rt^rt Fig. i-ix.— Terehratula dor- 

 of Terehratula. of the Chalk). sata (e.xterior). 



fossils in the rocks of Palaeozoic age. Hence their 

 great value to the geologist in helping him to diagnose 

 the strata where he happens to find them. Another 

 peculiarity about the Tala^ozoic Brachiopods is their 



