1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 455 



apparently furnish the best basis for comparison, the presence of 

 numerous representatives of Ncohipparion, Protohippvs, and Plio- 

 hippns gives an assemblage much more advanced than that of the 

 Barstow, in which only one form is referred to a genus more advanced 

 than Merychippus. On the other hand the predominance in the 

 Equidae of the Snake Creek fauna of forms of Merychippus near 

 those making up the great bulk of the horses of the Barstow area 

 suggests that the times of deposition of some portion of the Snake 

 Creek and of the Barstow were not separated by a wide epoch. 



In the Carnivora the Snake Creek possesses an advanced element 

 in certain Aeluroclon species, which may not be much more progres- 

 sive than some seen in the Barstow. With this element at Snake 

 Creek are Tephrocyon species, near if not identical with those of the 

 Barstow. 



In the artiodactyls, Dromomeryx is represented in the two areas ; 

 Merycodus is represented by closely related forms in Snake Creek 

 and Barstow ; the relatively primitive Blastomeryx is known at Snake 

 Creek, but not as yet in the Barstow ; certain camels at Snake Creek 

 are presumably somewhat more progressive ; and the appearance of 

 Neotragocerus is probably an advanced character of the Snake Creek 

 assemblage. 



A part of the Snake Creek fauna is certainly more advanced than 

 the Barstow, but connecting elements seem to indicate a shorter lapse 

 of time between the Barstow and a portion of the Snake Creek than 

 between the Barstow and Bicardo, as this part of the Snake Creek 

 fauna though more widely removed geographically than the Ricardo 

 is nearer to the Barstow in composition. 226 



Description op Fauna 

 testudinata 



Testudinate remains are not uncommon in the Barstow beds, but 

 usually consist only of small fragments. Two specimens represent 

 the greater part of the carapace and plastron, and a third shows 

 important parts of both carapace and pastron. So far as known 

 all of the material obtained represents land tortoises allied to the 

 Recent genus Testudo. This group is represented in the Mohave area 

 at the present time by the desert tortoise Gopherus agassizii. Two of 

 the Miocene specimens greatly exceed the living form in size. 



22ft See recent discussion of this question by W. D. Matthew, Contributions to 

 the Snake Creek fauna, with notes upon the Pleistocene of Western Nebraska, 

 American Museum Expedition of 1916, Bull. Amer. Mus. Nat. Hist., vol. 38, pp. 

 183-229, pis. 4-10, 1918. 



