52 



BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



[Toim 



Tlie oldest of these I have called the Eryops beds, from the most abun- 

 dant genus of Labyrinthodonts which is found in it. They contain, also, 

 abundance of other Vertehrata, none of which are higher than Beptilia 

 (order Theromorplia)^ with plants, mollusks, etc. They consist of sand- 

 stones, alternating with beds of red clay and coarse conglomerate and 

 sphserosiderite, etc. They are chiefly distributed in Northern Texas 

 and Southern Indian Territory. 



The Gleiisydrops shale, named by me in 18G5, forms a thin stratum, in 

 Southeast Illinois and Southwest Indiana, consisting of black and rarely 

 reddish carbonaceous sliales and clays. These appear in some places to 

 lie conformably on the Coal-Measures, to which they have been referred 

 by previous geologists, but CoUett, Gibson, and others have shown that 

 it is unconformable over considerable areas. It does not belong to the 

 Coal-Measures. 



The Puerco marls were first observed by me in IN^ew Mexico in 1874, 

 and afterwards found to have an extensive development in Southwestern 

 Colorado, by Endlich, in 1875. He has referred them to the lowest place 

 in the Tertiary series, but the absence of fossils renders it difficult to 

 conclude whether they belong here or in the Laramie series. 



The Oregon White Eiver beds difterfrom those found east of the Eocky 

 Mountains, although they contain a majority of the same genera, and 

 many of the same species. They are wanting in the important genera 

 Symhorodon and Menodus. To represent these genera^ they have Dceo- 

 don, and, in addition, some peculiar genera of Bodentia, as Entoptyclms, 

 Fleurolicus, and Ileniscomys, and the Suilline Falwochcerus. Among Car- 

 nivora, the genus Enliydrocyon is, so far as known, characteristic of them. 



The Loup Fork beds are represented in the valley of Smith's River, 

 Montana, by a horizon which may be somewhat older than that hereto- 

 fore known. The fauna presents us with the typical genera Frocamelus, 

 Hippotherium, ProtoMppus, Mastodon, and MerycocliceruSj but, in addition, 

 with the peculiar genera of Oreodontidce, TiclioleptuSj Cyclopidius, and 

 PitJiecistes,* and with Euminants similar to PaUeomeryx. These are 

 wanting from the other parts of the formation, and I therefore name the 

 two divisions the Ticholeptus and the Procamelus beds. 



I have already mentioned the Megalonyx beds as the equivalents in 

 the east of ]S"orth America of the Equus beds of Oregon and Califor- 

 nia, but which present such important differences that they cannot be 

 identified. The differences are displayed in the catalogues already given, 

 the list of the Megalonyx fauna having been derived from the explora- 

 tion of caves in Pennsylvania t, Virginia, and Illinois. The remains of 

 this fauna are by no means found in caves only, but are found in swamps 

 and Pliocene clays. The extinct genera characteristic of the Megalonyx 

 beds are Megatherium, Megalonyx, Gastoroides, and ArctotJierium ; the 

 genera no longer living in Korth America, Hydrochoeriis, Tapirus. 



* Proc. Am. Philos. Soc. 1877, p. 219. 

 t Loc. cit. 1871, p. 73. 



