ccviii GENERAL SUMMARY OF SCIENTIFIC AND 



The extensive and very fully illustrated work by Professor 

 Cope, entitled "The Vertebrata of the Cretaceous Forma- 

 tions of the West," published in the Reports of Hayden's 

 United States Geological Survey of the Territories, is re- 

 plete with new data regarding the wonderful fauna which in- 

 habited the ancient lakes of the far West. After giving in 

 an introduction his views on the significance of paleontolog- 

 ical science, he divides the work into three parts. The first 

 part is devoted to the classification and distribution of the 

 Cretaceous deposits of the West ; the second part contains 

 descriptions of the Cretaceous Vertebrata of the West ; while 

 the third part is occupied with a synopsis of the known Cre- 

 taceous Vertebrata of North America. The work is illus- 

 trated with fifty-seven lithographic plates. 



It has been stated, says Cope in this work, that the life of 

 the present period in the Southern hemisphere is not homo- 

 geneous. The same is true, though in a less degree, of the 

 Northern. Thus, if we include India in the latter, the ele- 

 phant is a Pliocene form, and the true rhinoceros Upper Mio- 

 cene. In the Northern hemisphere the dogs are Miocene. 

 In North America, the opossum, and probably the raccoon, 

 are Eocene ; the wolves and foxes appeared in the Miocene 

 age, and the weasels in the Pliocene. Perhaps the cats first 

 appeared in the American Pliocene. Comparatively few 

 mammalian types mark, by their origin, the latest geologic 

 epochs. Such are the ruminants, as deer and oxen, with the 

 true horses, which all commence in the Upper Pliocene of the 

 Northern hemisphere. Finally, man alone signalizes the last 

 or glacial period, and is to reach his culmination in the ages 

 that intervene between that great time-boundary and one to 

 come. Thus a certain proportion only of the life of a given 

 epoch is characteristic of it that is, originates in it ; the re- 

 maining members being legacies from preceding ages. Hence 

 the latest forms of life embraced in an extinct fauna are the 

 true indicators of the chronological relations of that fauna. 

 The total number of North American Cretaceous Vertebrates 

 enumerated and described is 253, of which 97 are fishes, 147 

 reptiles, and 9 are birds. No mammals have yet been dis- 

 covered. 



Whether thoroughbred stock of old and well-established 

 herds ever reverts to the original type is called in question 



