/JV SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 



The late Professor E. D. Cope g-ave a list of one hundred 

 and forty known species of reptiles from the Cretaceous of North 

 America. 



This was the era of the introduction of Birds. There were 

 hirds with the long- vertebrated tails and toothed jaws of rep- 

 tiles ; next the Toothed Birds, entirely different from anv exist- 

 ing- order, which, instead of the horny beak characteristic of ex- 

 isting- birds, had thin, long, slender jaws, with many sharp, con- 

 ical teeth, set in sockets (Odontotornas) ; others with teeth set in 

 grooves (Odontalc^e) , and finally the true birds (Ornithes) of 

 the present time. 



The Fishes advanced in their evolution from older forms, 

 and the typical modern fishes were first introduced in the Cre- 

 taceous. 



Of the Mollusks, the Oysters and allied genera, the Aviculas 

 and Inoceramus attained to a great size, and there were immense 

 numbers of Ammonites, Baculites and Belemnites in great va- 

 riety, and of immense size. (The writer found an Ammonite 

 in Shasta County which was over two feet in diameter). 



The Ammonites died out at the close of the Cretaceous, after 

 taking upon themselves strange forms just previous to their ex- 

 tinction. 



These strange forms have been likened bv Agassiz to death 

 contortions — forms assumed in the attempt to adapt themselves 

 to the new environment, and thus to attempt escape from their 

 inevitable destiny. 



With the close of the Cretaceous, the huge marine reptiles 

 also became extinct, and their places were occupied by different 

 forms. 



The bodily upheaval of the entire western half of our con- 

 tinent, which abolished the great interior Cretaceous sea. re- 

 sulted in a correspondingly great change in climatic conditions, 

 and brought about an extraordinary change of life-system. This 

 has been called "a. period of rapid evolution, which characterized 

 and accompanied the dawn of the modern history of the earth.'" 

 (Le Conte). 



THE AGE OF MAMMALS. 



It may be remarked that no animals have been discovered 

 which can be considered as the progenitors of the Mammals. 

 Marsupials, which are of course Mammals, have been found in 

 the Jurassic, and still exist in some portions of the world. There 

 seems to be a gap in the procession of the Mammalia between 

 the Jurassic and the Tertiary, when possibly some conditions 

 existed on this continent which drove them to other regions, as 

 Nature does not repeat itself, nor is the type of an organism which 

 becomes extinct ever reproduced. 



In the Tertiary Period animals and plants typical of those 



