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Universitij of California Publications in Geology [Vol. 12 



to a marked degree the camel and equine hosts of our Pliocene of 

 long ago. Moreover, the conditions of this Pliocene were probably 

 very similar to those extant throughout a vast expanse of the desert- 

 encircled belt of the eastern highland of present Africa, where a slight 

 change in altitude with accompanying increase or decrease in humidity, 

 temperature, and vegetation, again and again witnesses the strangest 

 and most marked faunistic change. It may well be that some of the 

 gaps that seem to separate our few known Pliocene assemblages are the 

 result of such local distribution rather than of great lapse of time. 



At length local stream activity, stimulated through the gradual 

 elevation of the San Jacinto region, brought the Eden sedimentary 

 stage to an end. and caused its deposits to undergo a period of erosion. 

 This stream rejuvenation may have been due in part to an associated 

 subsidence of adjoining areas, as bedrock, which must in compara- 

 tively recent times have been subjected to aerial action, occurs today 

 only at some thousands of feet beneath the floors of adjacent valleys. 



At the close of the Eden erosion stage another but coarser series 

 of sediments were laid down, those of the San Timoteo beds. These 

 covered the flner Eden to a great depth. A striking character of 

 this later deposition is the banded appearance of the strata, due to 

 recurring coarser and finer materials, which suggest either alternations 

 of high and low relief or climatic change. The fauna of the time in 

 comparison to that of the Eden is little known, but was evidently of 

 most instructive transitional stage. The small and earlier t3^pes of 

 Pliohippus are replaced by more advanced horses; a large horse, and 

 a smaller animal that to a pronounced degree resemble the more pro- 

 gressive horses of the older Eden race. Ground-sloths, several camels, 

 antelope, and great tortoises are all represented in this fauna. 



The deposits of the Bautista Badlands, lying to the southwest of 

 Eden, are of later date. They were evidently accumulated in part in a 

 playa-like lake as a series of fine, worked-over fanglomerates and clays- 

 derived from the low highlands of the immediate north and east. 

 The late Pliocene inhabitants of San Timoteo had in their turn passed 

 away, for in this great deposit are seen collected the remains of a 

 new faima, though again of mixed forest- and plains-grazing type. 

 The horse is fully as advanced as that which occurs in the Rancho 

 La Brea asphalt deposits, and perhaps with the associated antelope, 

 deer, camels, and ground-sloth represents even a slightly later stage 

 than that indicated by the Rancho La Brea fauna. 



