PALEONTOLOGY. 403 



No. 199, U. S. Geol. Surv.). Formerly a great lake, in some places 

 more than 100 miles wdde, occupied the valley and continued on until 

 late Pliocene time and even into the Pleistocene. Toward the end of 

 its existence vast sheets of lava were poured over the accumulated 

 deposits of sand and gravel. On Russell's map somewhat more than 

 the upper half of the valley is marked as covered with lava; the lower 

 half is represented as occupied by Tertiary lake-beds; but in these are 

 also intercalated lava-sheets. These lake-beds have been referred by 

 geologists and palaeontologists to the Pliocene. 



In 1883 Cope described from these upper lake deposits numerous 

 species of extinct fishes; and he gave the beds the name Idaho forma- 

 tion, referring it to the Pliocene. He called attention to the fact that 

 these beds had furnished also remains of mastodon (Stegomastodon 

 mirificus), a horse, and a megalonyx. Since then Dr. John C. Merriam 

 has reported from apparently the same deposits a new saber-tooth 

 tiger, a new antelope, a new horse, and a rhinoceros. At various places 

 in the upper half of the valley the writer has evidences of the discovery 

 of horses, camels, Elephas columhi, E. irnperator, and bisons. In several 

 cases these have come from deposits underlying sheets of lava. They 

 belong at latest to the first interglacial (Aftonian), and probably to the 

 Idaho formation. 



Other discoveries of animals recognized to be of Pleistocene age in 

 apparent association with genera otherwise known only from the Plio- 

 cene have been made in Florida and Oregon. In such cases it has been 

 assumed that there has occurred, either before or after exhumation, 

 a commingling of faunas of two different ages. From a small cave in 

 Coconino county, Ai'izona, the writer has studied a collection contain- 

 ing many animals, among them horses, which are of common occurrence 

 in the Pleistocene; but with them come two species of camels of the 

 genus Procamelus. These are closely related to two species found in 

 Florida mingled with Pleistocene animals, but they have been referred 

 to the lower Pliocene or even the upper Miocene. No mingling of 

 faunas had occurred in the Arizona cave, and it now becomes prob- 

 able that none had occurred in the other cases referred to. The writer 

 beUeves, therefore, that the vertebrates of the Arizona cave, of the 

 Idaho formation, and not unlikely those of the Florida and Oregon lo- 

 caUties, all belong to the Pleistocene, but to an older Pleistocene than 

 the Aftonian. It seems necessary to refer this older fauna to the oldest 

 Pleistocene, that corresponding to the first interglacial stage. Nothing 

 about this fauna has hitherto been known. 



Further evidences have been received during the year that the lowest 

 lands along the Gulf of Mexico have undergone little or no submergence 

 since the early Pleistocene. Remains of an Elephas columhi, of a 

 species of Gomphoiherium, and of a camel have been found in Texas at 

 the edge of salt water and buried only a few feet above sea-level. 



