66 



Tremadoc Slates. 



the genera Palcearca, Glyptarca, Davidia, Modiolopsis, 

 and others, also Theca operculata, and other Pteropoda, 

 and several species of Bellerophon occur (J?. Arfonensis, 

 &c.), together with Cephalopoda, viz., Orthoceras seri- 



FIG. 17. 



Niobe Homfrayi. Palaearca Hopkinsoni. Orthis carausii. 



Group of Tremadoc Slate Fossils. 



ceum, and Cyrtoceras prcecox ; also Encrinites, and a 

 starfish, Palasterina Ramseyensis. Altogether, as 

 now known, the life of the time was richer than that of 

 the Cambrian and Lingula flag strata, but all of these 

 faunas are probably very imperfect and fragmentary in 

 the British area. 



