FEATURES IN HISTORY OF LIFE ON PACIFIC COAST 



MAMMALIAN FAUNAS OF THE GREAT BASIN PROV- 

 INCE. Within the limits of the Great Basin Province 

 the most important series of mammalian faunas is 

 that in the John Day region of eastern Oregon. In 

 this area the Cenozoic section from the base up- 

 ward comprises the Glarno Eocene, John Day Oligo- 

 cene, Lower Miocene Columbia lava flows, Mascall 

 Middle Miocene, Rattlesnake Pliocene, and terrace 

 deposits of the Pleistocene. All of these formations, 

 excepting the lavas, contain remains representing 

 the extinct life of this region. The Eocene has an 

 abundant flora but contains no remains of mammals. 

 Mammal remains are found in all of the formations 

 above the Eocene. 



The mammal fauna of the John Day Oligocene 

 includes a little more than one hundred species, of 

 which an unusually large number of forms belong 

 to the cat and dog groups. Of the dog family there 

 are at least 18 species distributed among 9 genera. 

 Of the cats there are at least 10 species, representing 

 4 or 5 genera referred to the sabre-tooth group. 

 Numerous primitive horses belong to the genus 

 Miohippus. Rhinoceroses are represented by the 

 two-horned Diceratherium and the hornless Acera- 

 therium. The gigantic pig-like Elotherium is known 

 by a number of fine specimens. Smaller pigs of the 

 peccarv type are not uncommon. The most abun- 

 dant remains in all of this fauna are those belonging 

 in several genera of the characteristic even-toed 

 ungulates, the oreodons. Primitive camels are well 

 known, especially in the upper portion of the series. 



The fauna of the Mascall Middle Miocene is less 

 satisfactorily known than that of the John Day, and 

 contains a considerable variety of horses belonging 

 in at least three genera, of which the three-toed 

 Merychippus is the most common and characteris- 

 tic type. The camels are much larger and more 

 specialized forms than those of the John Day. The 

 members of the cat and dog families are all differ- 

 ent from those of the John Day. 



The Rattlesnake Pliocene fauna is imperfectly 

 known. It contains horses of the Neohipparion 

 and PUohippus groups, approaching in many re- 

 spects the type of structure in modern horses. There 

 is also a very large camel, a rhinoceros, and a large 

 peccary. 



The Pleistocene fauna of the John Day is not 

 well known, but contains the remains of elephants 

 of a very modern type. 



On the northern border of the Nevada region are 

 two important series of mammal beds known as the 

 Virgin Valley and Thousand Creek formations. The 



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