The Swifts 



Sub-division b. Enlarged scales of the back in four, regular 



rows two rows on each side of a central row (or two) of 



minute scales. A row of enlarged, bristling scales on each side. 



WHITE-BELLIED SWIFT, U. symmetrica, Baird. 



Head proportionately broad and flat. Hind limb as long 



or longer than the distance from the vent to the 



fold of skin under throat. Grayish or brownish, with 



darker, wavy cross-bands. Abdomen white; throat 



frequently yellow. Dimensions: Total length, 5^ 



inches; tail, 3f inches; width of body f of an inch; 



width of head, T V of an inch; length of head, an 



inch; length of hind limb, if of an inch. 



Distribution. Common in the desert regions of 



Arizona and eastern California. 



Sub-division c. Enlarged scales of back in from five to seven 

 regular rows of about uniform si^e. A series of but slightly 

 enlarged and scattered, conical scales on each side. 



BLACK-TAILED SWIFT, U. nigricauda, Cope. 

 Brown or gray, with wavy, black cross-bands. Tail black- 

 ish. Throat of the male orange. One of the smallest 

 species total length, 3! inches; tail i|| of an inch. 

 Distribution. Lower California. Abundant. 



BLACK SWIFT, U. parviscutata, Van Denburgh. 

 Sooty black above, with a few, irregularly scattered, light 

 dots and indications of cross-bands of a deeper black. 

 Male specimens differ from the preceding, to which this 

 species is closely related, in possessing a blue patch, 

 in place of orange, on the throat. Attains a length 

 of 4! inches; tail occupying 3^ inches of that measure- 

 ment. 

 Distribution. Lower California. Rare. 



LONG-TAILED SWIFT, U. graciosa, Hallowell. 

 The most slender species of the genus. Tail excessively 

 long two and a half times the length of the combined 

 head and body. Ashy-gray or reddish, with a series 

 of darker, wavy cross-bars on each side. A band ex- 

 tending lengthwise on neck. Males with a blue patch 

 on each side of the abdomen. Attains a length of 

 eight inches, of which the tail occupies 5! inches. 

 Distribution. Arid regions of southern Nevada, 

 Arizona and eastern California, in the vicinity 

 of the Colorado River. 



Habits. The Small-scaled Swifts are terrestrial lizards, 

 living among rocks in the deserts and sub-arid regions of the 

 Southwest. They are wonderfully agile and fairly skim over 

 the ground when pursued, but do not appear to adopt the habit 



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