LIFE ON THE EARTH. 89 



Annelida. In the modern seas we find two great 

 groups, Cephalobranchiate and Dorsibranchiate An- 

 nelida. The same two orders exist in the Lower 

 Palaeozoic Strata, sometimes containing species of 

 very large dimensions, and they seem to have been, 

 as now, mostly prevalent on muddy shores. 



Cirripedia These beautiful animals are not re- 

 cognized in Palaeozoic Strata. 



Crustacea. Dividing them into two groups we 

 find one (Entomostraca) extremely prevalent in the 

 Palaeozoic periods; the other (Malacostraca) not yet 

 certainly discovered therein. 



Among the Entomostraca the large groups of 

 Trilobitidae and Eurypteridae are peculiar to the 

 Palaeozoic ages. 



The relations to time which thus appear among 

 the Articulata are represented in the following 

 Table. 



