116 University of California Publications in Geology [Vol.10 



COMPOSITION AND RELATIONSHIPS OF MAMMALIAN 

 FAUNA OF THE CHANAC FORMATION 



The representation of mammalian forms obtained in the land- 

 laid beds of the Chanac formation is very scanty, but it includes more 

 and better preserved material than that upon which the first note was 

 based. Following' is a list of the forms now available : 



Bhinocerotid, indet. 

 Protohippus tehonensis Merriam. 

 Neohipparion gratum tehonense 

 Merriam 



Neohipparion, near molle Merriam. 



Prosthermops, sp. 

 Camelid, indet. large. 

 Meryeodus, near neeatus Leidy. 

 Proboscidean (Tetrabelodonf), indet. 



The general aspect of the small assemblage of forms now known 

 is not materially different from that originally suggested. It is clear, 

 however, that the most commonly encountered horses of this fauna 

 represent the genus Hipparion. The best-known teeth are those of 

 two small forms, Neohipparion gratum tehonense, closely resembling 

 Neohipparion gratum of the Great Plains region; and a form closely 

 approaching Neohipparion molle found in the lower portion of the 

 Jacalitos-Etchegoin Pliocene section of the North Coalinga region. 

 Horses closely resembling those of the Tejon Hills region have been 

 found by R. W. Pack in late Tertiary beds on the eastern flank of 

 the Mount Diablo Range, southwest of Modesto. Of the Hipparion- 

 like horses known in the faunas of the Mohave Desert region, the type 

 most closely approaching the Tejon Hills form is found in an unde- 

 scribed species obtained in the upper portion of the Ricardo Pliocene 

 section. The Ricardo form does not, however, seem to be specifically 

 identical with that from the Tejon Hills. The Tejon Hills horse 

 described as Protohippus tehonensis has some resemblance to a form 

 found in the upper Miocene Barstow formation of the Mohave Desert, 

 but seems not to be specifically identical with the Barstow form. The 

 Tejon Hills Protohippus also shows similarity to a species known in 

 the lower portion of the Jacalitos-Etchegoin section of the North 

 Coalinga region. 



The rhinocerotid and mastodontine remains from the Tejon Hills 

 furnish no definite evidence as to age. Rhinoceroses are well repre- 

 sented in the Thousand Creek and Rattlesnake Pliocene of Nevada 

 and Oregon, and are known in the Pliocene of the Pinole Tuff type 

 section in San Francisco Bay region of California. It is interesting 

 to note that as yet no remains of rhinoceroses have been secured from 



