The Swifts 



scale rows apart, while male specimens have two bluish patches 

 on the throat in place of one, as is usually the case with the com- 

 mon species. Moreover, the abdominal plates of this lizard are 

 keeled; in this character it is unique among all the species of the 

 genus. It is of small size. 



Distribution. Apparently restricted to southwestern Texas. 



The Striped Swift, Sceloporus scalaris, (Wiegmann), should 

 be enumerated among the moderate-sized species. The head 

 plates are strongly wrinkled and the scales of the body are small, 

 narrow and sharply pointed. 



Olive gray, with a very narrow, but vividly defined stripe 

 of yellow or white on each side of the back, extending along the 

 centre of a single row of scales. These stripes are separated by 

 about six or seven scale rows. Two rows of dusky crescents 

 on the back. 



Resembles the sage-brush swift, (5. graciosus), of Division 

 D, and several other species that have pronounced, pale bands 

 on either side of the back, but may be distinguished by the very 

 narrow bands, traversing the centre only, of a single row of 

 scales. On the other species the bands either cover the entire 

 width of a single row of scales, or embrace a half row of scales 

 each side of the former. The width between these bands (num- 

 ber of scale rows) is also an important point to be used in deter- 

 mination. 



The Striped Swift has a round, and jet black spot at the 

 base of the forelimb. 



Distribution. Southern Arizona and Mexico generally. 



Division D. In the fourth group of those species of Spiny 

 Swifts that occur within the limits of the United States, we 

 have our largest and most showy species and one other, of con- 

 siderably smaller size. With these two species there are two 

 rows of the large, supraocular plates over each eye, bordered 

 internally by a single row of smaller scales and externally by 

 one or two rows. 



The Collared Swift, Sceloporus iorquatus, variety poinsettii, 

 (Baird & Girard),is a northerly phase of a Mexican species. It 

 is characterised by a broad, jet-black collar, bordered on each 

 side with yellow and extending entirely around the upper surface 

 of the neck. 



The general proportions of this fine swift are illustrated by 



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