92 Dynamic Theory. 



flourished in Greenland and Northern Europe in the Miocene. There 

 were local causes also favoring the growth of protophyte algae Diatoms 

 in certain places. 



These minute plants have left their Siliceous shell remains in great 

 beds. One in Bohemia is fourteen feet thick ' ' and ever} 7 inch of the 

 material according to Ehrenberg ' contains 40,000,000,000 shells."* 

 Another bed in Virginia is 30 feet thick and many miles in extent. 

 Another deposit in California is 50 feet thick. These deposits were in 

 part or wholl}', fresh water deposits. 



The animal genera of the Tertiary period are also chiefly those of the 

 present, although species have greatly changed. Protozoa had a great 

 representation. Nummulites, a Rhizopod family, built by the accumu- 

 lation of their calcareous shells, limestone strata many thousand feet 

 thick during the Eocene epoch in central and southern Europe, Asia 

 and the central part of the United States. 



Of insects all the orders were represented in the Miocene. In Switz- 

 erland 100 species of winged ants have been found none appearing 

 wingless. Le Conte judiciously observes that this must have been be- 

 fore the time when the female and neuter ants developed their present 

 peculiarities, and both sexes remained winged alike during life. They 

 were more numerous than now in Europe and were of tropical species. 



1 ' There are crabs and insects of nearly all the modern tribes except- 

 ing the higher group among the crabs, viz., the Maioid or Triangular." 6 



' ' Teleosts were first introduced in the Cretaceous, but only in the 

 Tertiary did they become very abundant. Ganoids on the contrary be- 

 came fewer in number and they sank into their present subordinate po- 

 sition, f Among the Placoids the Hybodonts are gone, the Cestracionts 

 are few in number, but the Squalodonts reach their maximum develop- 

 ment both in number and size. "* 



The great Saurians, Enalio-Saurs, Dino-Saurs, Moso-Saurs and Ptero- 

 Saurs all became extinct in the Jurassic and Cretaceous. The represen- 

 tative reptiles of the Tertiary are ^crocodiles, turtles and snakes. There 

 are some large Salamandroid Amphibians, ome of which was four feet 

 long v In none of these orders did the present characteristics prevail in 

 the Tertiary, but they have been more or less differentiated and finished 

 up since. (All the Tertiary species of vertebrates including Fishes, 

 Reptiles, Birds and Mammals are now extinct and we have other species 

 in their places. ) 



The same sort of changes go on with reference to the birds. There 

 were birds of strong reptilian characteristics and some wading birds in 

 the Cretaceous era. In the Tertiary great improvements Appear in 



4 Le Conte 484. 5 Dana 514. t The modern Ganoids are fresh water fish only. 

 *Le Conte 491. 



