504 



Scientific Intelligence. 



8. Tertiary Mammal Horizons of North America; by Henry 

 F. Osboen. Bull. Amer. Mus. Nat. Hist., xxm, 1907, pp. 

 237-253. — This is one of the most valuable geological summaries 

 of our present knowledge of North American mammal horizons. 

 The thickness of these Tertiary strata is over 18,000 feet. The 

 major facts may be tabulated as follows: 



Seventh mammal 

 phase. Increas- 

 ing cold, moist- 

 ure, and forests. 

 Another but 

 gradual Euras- 

 ian intermigra- 

 tion. Much ex- 

 tinction of pre- 

 vious native 

 stocks. 



Provisional 

 correlations 

 with other 

 countries. 



Lower Pleistocene or Preglacial. 

 Sheridan or Equus beds. 



Sixth mammal 

 phase. Inter- 

 migrations with 

 South America. 



Upper Pliocene development as yet 

 not recognized in America. 



Middle Pliocene. Blanco or Glypto- 

 therium beds. Up to 3,000 feet. 



Sicilien. 

 Astien. 



Fifth mammal 

 phase. Inter- 

 migration with 

 Eurasia. In- 

 crease of sum- 

 mers droughts. 



Lower Pliocene. Republican or 



Peraceras beds 100 feet. 

 Upper Miocene. Loup Fork or 



Protohippus beds. Up to 120 



feet. 

 Lower Miocene. Ticholeptus beds. 



Up to 1,000 feet. 



Messinien- 

 Plaisancien. 



Tortonien. 



Langhien- 

 Helvetien. 



Fourth mammal 

 phase. First 

 Great Plains 

 forms. Second, 

 or Lower Oligo- 

 c e n e intermi- 

 gration with 

 western Eu- 

 rope. 



Transitional to Miocene. Arikaree 

 or Prornerycochcerus beds. Up 

 per John Day 400 feet. 



Upper Oligocene. John Day or 

 Diceratherium beds. Mountain 

 fauna. Up to 1,000 feet. 



Middle Oligocene. Upper Brule 

 or Leptauchenia beds. Lower 

 John Day. Up to 300 feet. 



Middle Oligocene. Lower Brule 

 or Oreodon beds. 



Lower Oligocene. Titanotherium 

 beds. 200 feet. This and the 

 Lower Brule horizons have de- 

 cided European affinities in the 

 Perissodactvla. 



Langhien- 

 Aquitanien. 



Aquitanien. 



About 

 Stampien. 



?Ludien in 



part. 



Sannoisien. 



