THE ORIGIN OF MAN 45 



ids in great variety. Brachiopods, bryozoans and 

 cup corals were also abundant but none attained 

 the profusion of the crinids. Large sharks were 

 becoming more and more plentiful and among 

 cephalopods, the nautilids were no longer so pre- 

 valent as thej' were in earlier times. Their des- 

 cendants, the goniatites, were more common than 

 in the Devonian, and the trilobites were almost 

 gone. The carnivorous or aggressive life of the 

 Waverlian sea was therefore dominated by the 

 pavement-toothed sharks. Of land life little is 

 known other than plants and as I shall not discuss 

 plant life, I shall refer the reader, if he be inter- 

 ested in the evolution of plant life, to a text-book 

 on Historical Geology. 



The marine life of the Tennesseian time differs 

 in many ways from that of the Waverlian, but as 

 it is largely a direct outgrowth of the latter it 

 naturally cannot vary greatly. The crinids were 

 no longer so diversified as in the preceding epoch, 

 but the two other groups of echinoderms were 



