June, 1912. New Titanotheres — Riggs. 25 



also beds of fresh-water clams. Reeds, leaves, and branches of trees 

 are abundant in the upper sandstone in association with representatives 

 of the upper fauna. 



The Amynodon Beds represent a transitional stage both in their 

 stratigraphy and in the characters of the fauna. The river sandstones 

 rapidly give place to shales and clays. Fossils occur in the heavier 

 sandstones very much as in the Upper Metarhinus Beds; at the same 

 time they become more abundant in the shales and clays as we pass 

 upward in the series. In the lower sandy shales but few evidences of 

 mammals are recognized, though in certain narrow strata fragments of 

 Eobasileus occur with comparative frequency. The lenticular sand- 

 stones, apparently of quiet water deposition, are rich in the remains 

 of low-ground mammals such as Amynodon, Sthenodectes and Dolicho- 

 rhinus. These sands show little evidence of water currents. Skulls 

 with mandibles and parts of skeletons are found associated. 



The gray clays yield a mixed fauna of lowland and plains forms. 

 Dolichorhinus and Amynodon are common; other genera recognized 

 are Uintatherium (?), Stylinodon and Protylopus. Little attention 

 was given to these beds. It is probable that a careful search would 

 reveal a much larger number of fossil forms than are here recorded. 

 The massive sandstones forming the upper series of the Amynodon 

 Beds yield Amynodon and Dolichorhinus as the most characteristic 

 fossils. Protelotherium and Crocodilus are also recorded from them. 



The Upper Uintah Beds (Horizon C) are not included in this recon- 

 noissance. It may be noted that this series is ushered in by an even 

 more marked transition than the last. Red clays and friable sand- 

 stones predominate. Massive sandstones are rare and of limited 

 extent. The fauna is known from the researches of Marsh, Scott, 

 Osborn, Hatcher and Douglass. 



Subfamily DOLICHORHIN^ 



Middle Eocene titanotheres having nasals elongate and deeply 

 recessed laterally, face shorter than cranium, an infra-orbital process 

 more or less developed, and molars only moderately expanded. 



This group is proposed in order to designate those long-nosed 

 titanotheres which evidently sprang from a common stock and form a 

 natural and homogeneous group. It includes the following genera: 

 Mesatirhinus Dolichorhinus 



Metarhinus Rhadinorhinus 



