526 GEOLOGY. 



forms necessary to make up a self-sustaining assemblage. There 



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Fig. 237. — The two upper curves in this diagram, shown in the Paleozoic periods, 

 and their continuation in the Mesozoic, constitute the evolution curve of the entire 

 class, Crinoidea. The two lower curves in the Paleozoic periods represent the 

 evolution curve of the order Camerata of the class Crinoidea, the order becoming 

 extinct just before the close of the Paleozoic. The discontinuity of the lines across 

 the Permian column, P, represents the imperfection of our knowledge of the Permian 

 faunas, and not that the crinoids became extinct in the Pennsylvanian, C, to reap- 

 pear in the Trias. In all the curves, the dotted line represents the number of 

 new genera initiated, and the full line the total number of genera present, the 

 difference between the two representing the number of genera which passed over 

 from the preceding period. The data for the curves have been compiled from the 

 publications of Wachsmuth and Springer. 



was beyond doubt an ample marine flora, but it made only a feeble, 

 obscure record. 



The Waverly Fauna, 



Contemporaneous with the evolution of life in the successive Kinder- 

 hook and Osage seas, there was a rather more provincial development 

 in the gulf east of the Cincinnati axis. There was no definite barrier 

 between the gulf and the sea on the west, but, owing partly to the 

 partial separation and more perhaps to the physical conditions, the 

 fauna in the Waverly gulf was sufficiently distinct to warrant separate 

 recognition. 



The Waverly fauna was characterized negatively by the rarity 

 of both corals and crinoids, the apparent reason being their depend- 

 dence on clear seas. To this there was one notable exception. At 

 Richfield, Ohio, there flourished a crinoid field occupied by the species 

 of several genera. These genera were also represented in the Osage 

 sea to the west, but the species there were wholly different. Appa- 



