LIFE ON THE EARTH. 73 



The Crustacea are nearly all Trilobites. 



Among the Brachiopoda is no Rhynchonella or 

 Terebratula. 



The single Monomyarian is Ambonychia Triton, 

 from Bird-hill, near Llandeilo, of the family Avicu- 

 lacese. 



The two Dimyarians are Ctenodonta Isevis and 

 Cucullella Anglica (of the family Arcadse). 



These two families stand near to one another in 

 the methods of naturalists. 



Among the characters of this period is the rela- 

 tive prevalence of Pteropod and Polyzoan species, 

 and the absence of Echinodermata, if indeed the 

 Haverfordwest Strata which yield Echinosphserites and 

 Sphseronites, be rightly removed from this formation. 



The Carnivorous tribes are augmented by the 

 Cephalopoda, which henceforward are found to sus- 

 tain a very important part in the economy of the 

 sea, and in a less degree by the Pteropoda and Hete- 

 ropoda. 



A third combination may be examined in the 

 Caradoc formation, which indeed is scarcely to be 

 separated from the Llandeilo series, but is much 

 richer in species. 



*Amorphozoa ... 2 genera 3 species. 



Zoophyta 11 23 



^Echinodermata.. 8 ..20 



