Vol. 6] Baker: Cenozoic History of the Mohave Desert. 357 



than they are persistently bedded ; their degree of induration 

 varies locally ; and they merge northward into the alluvial debris 

 of the Sierra Nevada slopes, from which they can scarcely be 

 distinguished in color, composition, and texture. Bones of mery- 

 codonts, horses, and camels were picked up along the foot of the 

 bluffs one-eighth to one-quarter mile west and northwest of 

 Ricardo postoffice. 



AGE OF THE KOSAMOND SERIES 

 Organic remains have been found in all the members of the 

 Rosamond Series except the basal breccia. They were found 

 in each of the five localities examined. But in only the Barstow 

 syncline and Red Rock Canon were determinable fossils obtained 

 which serve to indicate the age of the containing beds. The 

 bones discovered in these two localities belong, according to 

 Professor J. C. Merriam, to mammals of the upper Miocene 

 period. 



ORIGIN AND MODE OF DEPOSITION OF THE ROSAMOND SERIES 

 The presence of fossil remains of characteristic fresh-water 

 gasteropods and of abundant cursorial and plains-living mam- 

 mals indicate that the strata of the Rosamond Series containing 

 these fossils are of terrestrial fresh-water and subaerial origin. 

 The fossil bones are checked and cracked as if they had been 

 exposed for a considerable time to the action of the sun, frost, 

 and abrupt changes of temperature, on the surfaces of an open 

 plains country. Nowhere was a complete skeleton of a mammal 

 found in place. Often remains of three or more different ani- 

 mals are mingled in the same deposit of fine material ; for ex- 

 ample, bones of horses, camels, dogs, and merycodonts. Horses 

 are the most common fossils, but camel and deer bones were also 

 quite abundant. Occasionally all or nearly all the bones of a 

 limb would be found together in their proper anatomical position. 

 Bones were also found in the breccia and conglomerate layers 

 where those of different species were apt to be mixed together 

 and to exhibit traces of wear. 



The constituents of the Rosamond Series have been derived 

 from two different sources : the one necessarily near the site of 

 deposition, and the other perhaps a considerable distance away. 



