358 NORTH AMERICAN FAUNA. [No. 7. 



Sacramento Valleys, reaching northward along the sides of Detrital 

 Valley for about 24 kilometers (15 miles) north of Mountain Spring. 



UTAH. 



Beaver dam Mountains. — Tree yuccas begin at the foot of the west 

 slope of the Beaverdam Mountains in southwestern Utah at an altitude 

 of about 700 meters (2,300 feet), and range up to 1,340 meters(4,400 feet), 

 forming a belt 8 or 9 kilometers (5 or 6 miles) in width. The trees 

 rarely exceed 3 meters (10 feet) in height and are more scattering than 

 in the Mohave Desert. 



Yucca elata? 



A narrow-leaved yucca provisionally referred to this species was 

 found sparingly in the Lower Santa Clara Valley, Utah, on the mesa 

 near the town of St. George, where it was in full bloom and very hand- 

 some May 11-15. Its flower- stalks are tall and slender, and its leaves 

 narrow and thin. A form resembling this, but with somewhat thicker 

 and heavier leaves, was found on the west slope of the Juniper Moun- 

 tains between Sheep Spring and Panaca, between the altitudes of 1,700 

 and 2,130 meters (5,800-6,700 feet). It was budding plentifully May 

 19, but was not found in flower. 



Yucca macrocarpa. (Plate xiv.) 



This large yucca was found in but few localities traversed by the ex- 

 pedition. It finds its western limit along with Opuntia ramosissima on 

 the North Kingston Mountains, between Besting Springs andPahrump 

 Valley, Nevada. It begins again on the east side of Pahrump Valley 

 at an altitude of about 970 meters (3,200 feet), and ranges up on the 

 west slope of the Charleston Mountains to 1,090 meters (3,600 feet), 

 forming a well-marked zone mixed with scattering trees of Yucca 

 arborescens, which latter species becomes more and more abundant 

 until it forms a true yucca forest in the upper Larrea and Coleogyne 

 belt, where Y. macrocarpa disappears. In this zone Yucca macrocarpa 

 grows larger than observed elsewhere, many plants reaching the height 

 of 2£ meters (8 feet), and some growing as high as 3 or even 4 meters 

 (10 to 13 feet). It never branches like Yucca arborescens but has a 

 heavy, irregular trunk, well shown in the accompanying photograph. 

 On warm soil a few plants were in full flower April 29, though most of 

 them were not yet in bud. On the east side of the Charleston Moun- 

 tains it begins at an altitude of 1,525 meters (about 5,000 feet), and 

 descends to the upper part of Vegas Valley, near Cottonwood Springs, 

 at an altitude of 900 meters (3,000 feet), where dozens were found in 

 flower April 30. 



On the north side of the Charleston Mountains this species occurs 

 sparingly throughout the higher parts of Indian Spring Valley above 

 1,180 meters (3,900 feet). It is common on the low divide about 27£ 

 kilometers (17 miles)' west of Indian Spring at an altitude of 1,220 

 meters or 4,000 feet, and thence is continuous westerly along the south 



