THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 363 



Mammals of the Blanco Formation. — The ' Blanco ' of Texas takes its 

 name from the httle mountain of white sand near the edge of the Llano 

 Estacado on Catfish Creek, which as a prominent landmark has been digni- 

 fied by the name of Mt. Blanco. (Fig. 1G8). 



The life phase of the Blanco is distinguished: (1) negatively by the 

 undoubted extinction of the Oreodontida^, a pliylum which we have ob- 

 served in its last stages 

 in the Lower Pliocene; 

 (2) by the apparent 

 extinction of the rhi- 

 noceroses; in all the ex- 

 plorations which have 

 been carried on in 

 these beds no traces 

 of these animals have 

 been found ; (3) by 

 the apparent but not 

 yet fully demonstrated 

 absence of the forest 

 or browsing horses of 

 the Hypohippus type. 

 No traces have been 

 found either of the 



grazing horses with short-crowned teeth, or of the Merychippus type. An- 

 other browsing mammal which has not yet been found in this zone is the 

 giraffe camel, or Alticamelus. 



Although the fauna is still imperfectly known, 

 Mastodons, brevirostral every branch of the mammals shows disappear- 



FiG. IGS. — American Museum eamp below Mt. Blanco, 

 Crosby County, Texas. ' Mt. Blanco ' is the white hill in the 

 distance. Glyptotherium Zone. Photograph by American 

 Museum of Natural History expedition of 1900. 



?Tetralophodont 



?Trilophodont 

 Stegodons 



S. mirificus 

 Grazing horses, 3 phyla 



Protohippus 



Pliohippus 



Neohipparion 

 Edentates 



Gravigrades 



Megalonychids ? 



Glyptotherium 

 Peccaries 



Platygonus 

 Felidse 



Felis 



ances as well as certain new arrivals which are 

 decidedly indicative of a new faunistic stage. 



Of marked zoogeographic interest is the first 

 appearance here of the giant glyptodonts, or 

 armored edentates of South American type; it is 

 of course impossible to determine whether these 

 animals entered the country about this time or 

 whether they had found their Avay there in the 

 Lower Pliocene, because at no period do the glyp- 

 todonts extend very far north. Accompanying 

 these armored edentates were the great hairy 

 gravigrade sloths related to the genera Megalonyx 

 and Mylodon, evidences of the existence of which 

 we have already found in the Lower Pliocent^ and 

 possibly in the Middle Miocene of North America. 



In Texas and Nebraska, and probably in some 



