The Swifts 



Sub-division II. Internal border of small scales, extending 



completely about the margin of supraorbital 



crescent. Sometimes an additional, but 



fragmental, external border. 



Gray, with wavy black cross-bands; an 



oblong, black patch on each shoulder; a 



broad, pale band on each side; size large; scales 



coarsely bristling. SPINY SWIFT, S. spinosus. 



Division B. A row of large, supraocular plates, with a 

 a single internal border and two external 

 rows of small scales. Larger head plates 

 smooth. 



Colour phases. Grayish or olive with wavy, dark cross- 

 bands. Usually a plate band (or two) on 

 each side. 

 Sub-division I . Traces of black collar on sides of neck. 



Bluish-black; a greenish or yellow spot in 

 each scale; a broad black collar on sides of 

 neck. Size large. YARROW'S SWIFT, S. yarrovii. 

 Sub-division II. No collar. Pale bands on sides. 



Greenish-gray, with two series of narrow 

 dark blotches (wavy) on back. Size moder- 

 ate.* Bands on sides obscure or lacking. 



WESTERN SWIFT, S. biseriatus. 



Dark green, with faint traces of a pale band 

 on each side. Scalation rather fine; size 

 small; apparently confined to southern Cali- 

 fornia and Lower California. 



VAN DEN BURGH'S SWIFT, S. vandenburgianus. 



Greenish-yellow, with obscure cross-bands; 

 a very distinct, pale band, on each side; scales 

 moderately coarse; size small. 



YELLOW-BANDED SWIFT, 



S. undulalus var. consobrinus. 



Division C. Very similar to Div. B. in arrangement of 

 the supraocular plates; but the larger plates of 

 the bead are wrinkled longitudinally (rugose). 

 There are occasionally three external borders of 

 small, supraorbital scales. 



Colour phases. Grayish, with darker cross-bands. No 

 collar. Pale bands on sides. 



* Species of this genus that attain an average length of nine inches, 

 may be termed large species; those reaching an average length of seven 

 inches may be considered as of moderate size, while species growing to a 

 maximum length of about five inches are designated as the small members 

 of Sceloforus. 



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