The Swifts 



character of the males. These exhibit a brilliant patch of blue 

 on each side of the abdomen. 



The species of Uia are exceedingly active — hence the popular 

 name of Swift. The general colouration is gray or brown, with 

 darker transverse bands or blotches. With individual speci- 

 mens, the ground colour and intensity of the pattern varies 

 greatly, according to light, temperature and the general activity 

 of the reptile itself. 



As this is a rather large genus and none of the species evinces 

 any marked differentiation of colours, the writer has prepared 

 a concise list of descriptions, which somewhat appeals to the 

 form of key employed elsewhere in this work. The divisions, 

 in this list, are based upon the formation of the scales of the 

 back. The key embraces only those species occurring in the 

 United States and Lower California.* 



Division I. Scales of the back small, smooth and of about 

 equal size. Scales of the tail small and smooth — not spiny. 

 This division contains the largest species: they attain a 

 length of tii'enty inches. 



Three black cross-bars on body. 



THREE-BARRED SWIFT, U. thalassina, Cope. 

 Body stout ; tail very long. Dark green, with three black 

 cross-bars. Abdomen greenish. Under side of tail 

 and limbs yellow. The largest and handsomest species 

 of the genus. Attains a length of 20J inches, of 

 which the tail forms 13J inch. 



Distribution. — Cape Region of Lower California. 

 Four black cross-bars on body. 



FOUR-BARRED SWIFT, U. rcpcns. Van Denburgh. 

 Very similar to the preceding, but with four black cross- 

 bars. The measurements of the type specimen are 

 smaller than those given for the Three-barred Swift. 

 Distribution. — Rare. Taken in Lower California. 

 Division II. Scales of the back, small, smooth and of about 

 equal size. Scales of the tail of much larger size — keeled 

 and spiny. mearns' swift. U. mearnsii, Stejneger. 



Body olive, with irregular, blackish cross-bands, between 

 which are pale spots. A jet black band across the 

 shoulders. Terminal third of tail blackish; remainder 

 brownish with wide, black cross-bands. Abdomen 

 greenish-white — bluish on the flanks. Attains a length 

 of about 9 inches; tail 6 inches. 



* In preparing this list, the writer has practically popularised Prof. 

 E. D. Cope's very complete, technical key to the genus Uta. 



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