CONTRIBUTIONS TO WESTERN BOTANY VI. 



BY MARCUS E- JONES. 



I. THE NAVAJO BASIN. 



I propose this name for that region, both botanically and zoo- 

 logically interesting, which occupies Southeastern Utah, South- 

 western Colorado, Northwestern New Mexico, and Northeastern 

 Arizona, whose limits are fairly well defined by the Colorada 

 River and its tributaries north of the entrance of the Grand 

 Canon (the junction of the Little Colorado and the Colorado) a& 

 far as the Book Cliffs on the north with a northern and narrow 

 extension along the Green River at least as far as the base of the 

 Uinta Mountains. Its western boundary is the base of the Coal 

 Range (Wasatch Plateau of Powell) in Utah, the Henry 

 Mountains, and the Buckskin Mountains on the southwest. Its 

 eastern boundary is the high country east of Grand Junction, 

 Colorado, extending thence east of south past the base of Mt. 

 SneflQes and thence along the edge of the mesa country through 

 Southern Colorado and south as far as Coolidge, New Mexico,^ 

 thence following the base of the northern slope of the MogoUons 

 and including the valley of the Little Colorado to the base of the 

 San Francisco swell near Caiion Diablo and thence north to the 

 Colorado River. This large and isolated region belongs almost 

 wholly to the Upper Sonoran of Merriam, and is to be considered 

 as a subdivision of that region with a fringe of the Transition 

 group on its edges. It has been isolated since the Miocene 

 Tertiary, or at least since the Pliocene with its present drainage, 

 and has been, surrounded on all sides by lofty and cold mountain 

 barriers from 7000 to 10,000 feet in average height above the 

 sea with the exception of a very narrow stretch of country only 

 a few miles wide and about 5000 feet above the sea from 

 Johnson, Ariz., and Kanab, Utah, to the Colorado River, which 

 connects with the narrow belts along the rivers belonging to the 

 Upper Sonoran. This narrow plateau belt below Kanab has 

 very few plants that might be classed as Upper Sonoran, but is 

 the lowest possible ingress to the basin except the precarious one 

 along the dark gorge of the river itself where there is very little 



February 21, 1894. 



