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 Colorado 
River and its tributaries north of the entrance of the Grand 
Cafion (the junction of the Little Colorado and the Colorado) as 
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. 
Sneffles 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 Mogollons 
and including the valley of the Little Colorado to the base of the 
San Francisco swell near Cafion 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. 
