The Swifts 



Dimensions. — Total Length . 5 inches. 



Length of Tail 2.V 



Width of Body | " 



Width of Head J " 



Distribution. — The Yellow-striped Swift is widely distrib- 

 uted. It occurs all over Texas and extends northward into 

 Nebraska, southward well into Mexico and westward into 

 Utah, Nevada and California. 



Group C. — The species of group C are very similar to those 

 of the preceding division and might appropriately be included 

 within it, but usually exhibit a wrinkling of the larger head 

 plates, which are corrugated in a longitudinal direction. With 

 a genus like the present one, beset with difficulties for the 

 beginner, we must take advantage of even such slight characters 

 to assist in unravelling the general tangle. The members of 

 this group show no trace of a black collar. 



The Variable Swift, Sceloporus variabilis, (Wiegmann), 

 has acquired its name from the difference in colouration between 

 the male and the female. The large supraocular plates are nu- 

 merous and narrow; they are bordered externally by two rows 

 of very small, almost granular scales. The larger head plates 

 are strongly wrinkled — rugose. The scales of the body are pro- 

 portionately small. 



Olive, or dark green, with a pale, greenish band on each 

 side; two rows of blackish spots on the back. The pale bands 

 are separated by about fourteen rows of scales. 



Male specimens have an elongated, black ellipse on each 

 side of the abdomen and a blackish band beneath the stripes 

 on the side. The females lack the abdominal black marking 

 and the dark band on the side as well. The species attains a 

 moderate size. 



Distribution. — In the United States this swift seems to 

 be confined to Texas; in that state it occurs as far north as San 

 Antonio. It is common in the eastern portions of Mexico. 



The Common Swift, Sceloporus undulatus, (Latrielle), one 

 of the smaller species. The scales are of moderate size, well- 

 keeled and moderately bristling; most specimens have the head 

 scales strongly wrinkled — rugose. 



Gray, sometimes brown or greenish, with narrow and wavy 

 black cross-bands on the back — often in the shape of irregular 



137 



