82 



CENOZOIC MAMMAL HORIZONS 



VI. SIXTH FATJNAL. PHASE. 



Land connection with. South. America reestablished — Invasion of South 

 American Edentata-Gravigrada and Glyptodontia — Migration of North 

 American mammals to South America. 



Decidedly distinct and more recent than either the typical ''Loup 

 Fork/' the upper ''Loup Fork" deposits on Republican River, 

 Kansas, or the Rattlesnake formation, is the Blanco formation of 

 Texas. 



MIDDLE PLIOCENE OR SECOND PHASE (EUROPE. ETAGE ASTIEN). 

 17. BLANCO FORMATION; GLYPTOTHERIUM ZONE. 

 (Fig. 15; PL I.) 

 HOMOTAXIS. 



North America. — Plains fauna : 1 , Blanco formation of Cummins," 

 Cope,^ Gidley*^ (100 feet), Llano Estacado of Texas. 2, Ogalalla 

 formation of Darton (? in part), northwestern Nebraska. 



BLANCO *ROCK CREEk" . 



(middle Pliocene) (Eqmiszone, lower Pleistocene) (zipper Miocene) 



I . f .„ 



PANHANDLE 



(rrtiddle A/iocene) 



CLARENDON 

 er Mii 



---4- 



Jurassic sandstone-. 



Fig. 15.— Diagrammatic section of the Staked Plains (Llano Estacado), Texas, showing the relations 

 of the "Clarendon "(or Protohippus zone), "Rock Creek" (or Equus zone), and Blanco (or Glypto- 

 therium zone) to the underlying "Panhandle" (or 1 Merycocharus zone). After J. W. Gidley, 1908. 



FAUN A. ^ 



This faunal phase is clearly characterized negatively: (1) By the 

 undoubted extinction of the Oreodontidae, (2) by the apparent 

 extinction of the Rhinocerotidae, (3) by the apparent but not yet 

 fully demonstrated absence of the forest or browsing horse Ilypo- 

 hippus. It is distinguished from the upper PHocene of Europe (etage 

 Sicilien) by being antecedent to the appearance of the genera Equus 

 and ElepTias. It is characterized very positively: In Texas (4) by the 

 first appearance of South American Edentata-Gravigrada, Mylodon, 

 Megalonyx; (5) also by the first appearance of Glyptodontia Glypto- 

 therium; (6) in Texas and Nebraska by short -jawed Proboscidea with 

 molar teeth in some respects resembling the Stegodon type, Dihelodon 

 mirijicus. 



a Cummins, W. F., Notes on the geology of northwest Texas: Third Ann. Kept. Geol. Survey Texas, 

 1891 (1892), pp. 129-200; Fourth Ann. Kept., 1892 (18^3), pp. 179-238. 



b Cope, E. D., A preliminary report on the vertebrate paleontology of the Llano Estacado: Fourth 

 Ann. Rept. Geol. Survey Texas, 1892 (1893 1, pp. 1-136. 



c Gidley, J. W., The fresh-water Tertiary of northwestern Texas, etc.: Bull. Am. Mus. Nat. Hist., 

 vol. 19, 1903 (Blanco^ pp. 624-632. 



d See Appendix, p. 91. 



