18 VEETEBRATA OF THE TERTIAEY. 



the Lodge Pole and South Platte slopes of the water-shed, appear to be 

 penetrated by numerous tortuous friable silicious rods and stem-like bodies 

 They resemble the roots of the vegetation of a swamp, and such they may 

 have been, as the stratum is frequently filled with remains of animals which 

 have been buried while it was in a soft state. No better-preserved remains 

 of plants were seen. The depth of the eiitire formation is not more than 

 75 feet, of which the softer beds are the lower, and vary in depth from one 

 foot to twenty. The superior strata are either sandstone, conglomerate, or a 

 coarse sand of varying thickness and alternating relations ; the conglom- 

 erate contains white pebbles and rolled Loup Fork mammalian remains. 



This formation rests on a stratum of white friable argillaceous rock of 

 the White River epoch, as represented in Fig. 6. 



The lithological characters above described are precisely those pre- 

 sented b3' the same formation in New Mexico.* 



Mr. King employs the name Niobrara for this formation, but Dr. 

 Hayden's namef was introduced many years previously. The new name 

 has also the disadvantage of being already in use for a horizon of the Cre- 

 taceous, which is well distinguished paleontologically. 



I have divided the Loup River formation into two divisions, on pale- 

 ontological gi'Ounds,J under the names of the Ticholeptus bed and the 

 Procamelns bed. The former occur in the valley of Deep River, Montana, on 

 the White River in Northern Nebraska, and in Western Nebraska, Avhere 

 it has been found by Mr. Hill. Its fauna presents in Montana a mixture of 

 fossils of the Procamelus horizon ; while in Nebraska, according to Hayden, 

 its typical genera are accompanied by White River mammalia. In the 

 former region, IlippotUerium, Protohippus, and Blastomeryx are mingled with 

 genera allied to Leptauchenia and with Merycochcerus. In Nebraska, Leptau- 

 chenia is said to be accompanied by Ischyromys, Palceolagus, Hyracodon, and 

 even Oreodon, genera which do not extend to the Procamelus bed. There 

 is, however, a question in my mind whether this collocation is entirely cor- 

 rect It is bed D of Hayden's section in Leidy's Extinct Fauna, Dakota and 

 Nebra.ska, p. 20. 



• So« l;i-|><>rt l.iriii. (;. M. Wbeolui-'n Kxplorations West of 100th Meridian, voLiv,p.283. 

 tSec Uana'fi Manual of Ocology, eilit. 18(;4, p. 511. 

 t Bull. U. 8. Geol. Surv. Toim, v, pp. 50-52. 



