78 



CEXOZOIC MAMM-\L HORIZONS 



Pla ins fau na. — Of local evolution on the Great Plains tlie Equidae 

 exliibit. as the most distinctive genus, the first of the Hippotheriinae 

 or MerycJiippus stage of horses with subln^psodont molar teeth: the 

 large brachyodont Hypoliippus is also found, as well as ParaJiippus. 

 Among RhinocerotidcT, the hornless ApTiehps first occurs, also TeJeo- 

 ceras. Among Tapiridae, Tapiravus. Among Camelidae, Miolahis 

 continues, Protolahis appears, and Alticamelus succeeds Oxydactylus. 

 Among OreodontidtP, the family reaches a climax of differentiation 

 in 7 genera, including Merychyus and Merycocharus, but adding the 

 ver\' characteristic genera TicJioleptus and Cyclopidius, wliicli are 

 probably direct descendants of Eporeodon and Leptauchenia of the 

 preceding stage. Among Rodentia-Mylagaulidae, Mylagaulus, Oera- 

 togaulus. Among Canidae, Cynarctus, AmpJiicyon, and other less 

 aberrant genera. 



Mountain Region fauna oftJie Mascall formation. — The Mascall for- 

 mation of Oregon, overlying the Columbia River lava and subjacent 

 John Day, is partly homot axial with the middle and upper Pliocene. 

 The fauna, sparsely kno^^^l, includes very primitive horses with 

 short-crowned teeth {ArchseoJiippus, ParaJiippus) ; also the more pro- 

 gressive MerycJiippus, which is characteristically middle Pliocene, 

 although it persists into the upper Miocene. TTe find Mioluhis among 

 Camelidae. Among Cervid^e, Pal^onuryx. Among Proboscidea, Tri- 

 lopJiodon. An ungual phalanx of the Edentata-Gravigrada type is 

 certainly reported from these beds (Sinclair): the true South Amer- 

 ican Gravigrada are first kno^^^l to occur in the middle Pliocene 

 (Blanco formation of Texas). 



MOUXTAIX REGIOX FLORA. 



The flora seems to point to a more recent age for these beds, but 

 American florae generally are more progressive than the vertebrate 

 fauna. The Mascall flora was considered upper Miocene by Lesque- 

 reux. Knowlton also concludes that the flora is of upper Miocene 

 age: from his list cited by Merriam* (1901), Hollick^ observes: 



I judge that the meteorological, climatal. and physiographic conditions indicated 

 would be comparable to those now met with on the Atlantic coastal plain at about 

 the latitude of the Carolina^. A majority of the trees, such as Salix, Quercus, Planus, 

 Aralia. Acer. Prunus. etc.. belong to the Temperate Zone, and represent a flora similar 

 to that of this \'icinity [Xew York, lat. 42° X.]. Accompanying these, however, are 

 a few of more southern distribution, such as Taxodium, Laurus. Sapindiis. and Ficusf, 

 which indicate that the flora as a whole should be regarded as warm-temperate. The 

 indicated moisture factor is a little more difficult to determine. MarsiUa is an aquatic 

 plant, and the characteristic habitat of Taxodium is swamp land, while the other 

 genera might represent either lowland or upland species. 



a Knowlton. F. H., FossU flora of the John Day basin: Bull. U. S. Geol. Survey No. 204, 1902, p. 108. 

 & Merriam, J. C, A contribution to the geology of the John Day basin: Bull. Dept. Geologj", Univ. 

 California, vol. 2. 1901. pp. 308. 309. 

 c Letter of February 6, 1906. 



