1917] 



Merriam: Pliocene Mammalian Faunas 



431 



Proboscidea 



Tetrabelodon?, sp. 

 Oreodontidae 



Merycoehoerus (Pronomotherium) californicus, n. sp. 

 Camelidae 



Procamelus, sp. a 



Procamelus, sp. b 



Pliauchenia, sp. 



Alticamelus ?, sp. 

 Bovidae 



Merycodus, near neeatus Leidy 



In contrast with other Pacific Coast and Great Basin faunas the 

 Ricardo is characterized by the presence of hipparions of an Old 

 "World type with Pliohippus, Merycodus, and an advanced oreodont 

 near Pronomotherium. The Ricardo is in every respect a less advanced 

 fauna than the Idaho. It is distinguished from the Thousand Creek- 

 Rattlesnake stage by the presence of Merycodus, and an oreodont ; by 

 the presence of hipparions with round protocone rather than the 

 Neohipparion type with flat protocone ; and by absence of highly 

 specialized antelopes and of rhinoceroses. The presence of such an- 

 cient types as Merycodus and an oreodoiit in the Ricardo indicates an 

 earlier stage than Thousand Creek-Rattlesnake from which these types 

 are absent. It is, moreover, possible that the Thousand Creek an- 

 telopes are descendants of the Ricardo Merycodus. Geologic evidence 

 tending to support the age determination based upon palaeontologic 

 data is found in the greater degree of induration and deformation of 

 the Ricardo. 



The Idaho beds of Oregon were named by E. D. Cope, 12 who de- 

 scribed from them a considerable series of fishes. Beds referred to 

 the Idaho extend over a large area bordering the Snake River Valley 

 in southwestern Idaho, and presumably reach into southeastern Ore- 

 gon. They are several hundred feet in thickness and exhibit a slight 

 degree of deformation at certain localities. The beds are generally 

 unconsolidated, but may show considerable induration and form steep 

 cliffs. Lindgren 13 collected a mammalian fauna from exposures pre- 

 sumed to he of the same age as the Idaho of Cope. The remains ob- 

 tained by Lindgren were determined as Pliocene by F. A. Lucas. 

 In the summer of 1916 collections were made at a number of localities 

 in this region by J. C. Merriam and J. P. Buwalda for the United 

 States Geological Survey. 



12 Cope. E. D., Proc. Amer. Philos. Soc, Nov., 1870, pp. 538-547; also Prop. 

 Acad. Nat. Sci. Phila., p. 125, June 26, 1883. 



is Lindgren, W., 20th Ann. Eep. TJ. S. Geol. Surv., pt. 3, p. 99, 1900. 



