130 CALIFORNIA ACADEMY OF SCIENCES. 



up by spots of the same color as the lines. In older 

 specimens these lines have become more or less obscure, 

 and in some specimens the upper surface is nearly uni- 

 color. The upper surfaces of the limbs are similarly 

 colored. The dark markings on the sides of the head 

 and neck and on the gular region are small and ill defined. 

 The tail is gray or brown, often with dark lines along 

 the keels of its upper scales. All the lower surfaces are 

 creamy white, usually suffused with gray or slate on the 

 gular region or chest, and maculated with black. 



Leiif^th to auus 47 61 82 83 92 9.3 



Length of tail 124 184 190 207 204 212 



Suout to ear 11 15 19 20 20 22 



Snout to interparietal 10 12 16 15 16 17 



Width of head 7 9 11 12 12 14 



Fore limb 17 24 29 31 32 32 



Hind limb 34 47 56 56 61 65 



Base of fifth to end of fourth toe 16 23 25 25 28 29 



Distribution. — The Desert Whiptail Lizard or " Swift 

 Jack " is common in many parts of the Mojave and 

 Colorado Deserts and the Great Basin, but does not 

 range farther west. It has been taken in Owen's, Coso, 

 Death, Panamint, and Deep Spring Valleys, in Inj'^o 

 County; at Mojave, in Kern County; Barstow, The 

 Needles, Leach Point Valley, and Warren's Wells, in 

 San Bernardino County; and Fort Yuma, in San Diego 

 County, California. Its range extends across Nevada 

 (Pahrump Valley, Oasis Valley, Pahranagat Valley, 

 vicinity Reno) to southern Idaho (Plains near Snake 

 River) and western Utah (Santa Clara and Great Salt 

 Lake Valleys). 



Habits. — This species lives on the open desert, over 

 which it runs with great swiftness. The sand banks 

 near The Needles are covered with its tracks, which end 

 in the holes made by small mammals. So far as I have 

 been able to learn, its food consists entirely of insects. 



