1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 449 



PALAEONTOLOGIC MATERIALS AVAILABLE 



Remains of Tertiary vertebrates are known from a wide area in 

 the Mohave region. They are not abundant in many places, but at a 

 few localities fragmentary specimens are found scattered over the 

 ground in considerable numbers. Connected parts of skeletons are 

 rare. At a number of points where bones were found in place in the 

 Tertiary sediments they were disconnected, and it is evident that the 

 mode of deposition of the beds, and of the accumulation of remains, 

 were such that skeletal parts were generally widely scattered and 

 broken or weathered before final burial. 



The preservation of teeth and bones available is commonly good ; 

 that is, the bones have not rotted nor broken down to a great extent 

 since burial. 



Horizontal distance represented about 5£ Miles 



Fig. 3. Somewhat generalized north and south section through the Rieardo 

 beds, extending from the basement complex of El Paso Mountain to the alluvium 

 of the Mohave Desert. Section prepared by J. P. Buwalda. 



The collections obtained represent several' thousand specimens, 

 mostly teeth and portions of limb bones. In a few cases good skull 

 material was secured. 



In the Barstow beds vertebrate remains are found almost exclu- 

 sively in the uppermost zone of the Barstow syncline as described by 

 Baker.- This division of the section was designated by Baker 20 as the 

 Fossiliferous Tuff member. In this portion of the section there are 

 occasional layers several inches in thickness containing an unusually 

 large representation of mammalian bones. One horizon of this nature 

 furnishing many remains of Merychippus, was known in the field as 

 the Merychippus bed or zone. Bones were found in the Resistant 

 Tuff member or fourth horizon, but were not discovered, so far as the 

 writer is aware, in the first, second, and third of the five members, 

 counting upward from the base of the section. 



In the Rieardo beds mammalian remains were found through the 

 greater part of the section. Good specimens are not abundant at 

 any horizon, but at a few localities fragments are common. At nearly 

 all horizons careful collecting will uncover a small representation of 

 the fauna. 



20 Baker, C. L., Univ. Calif. Publ., Bull. Dept. Geol., vol. 6, p. 345, 1911. 



