40. THAMNOPHIS 851 



Variation. Eight specimens have the loreal 1 1 in all. 

 The preoculars are 1 1 in all. The postoculars are 3 3 

 in two, 3 4 in two, and 4 4 in two. The temporals are 

 1+31+3 in four, 1+21+2 in three, and 1+32+3 in 

 one. The supralabials are 8 8 in twelve, 7 8 in one. The 

 infralabials are 1 1 1 in four, and 1 1 in two. The scale 

 rows are 21 19 17 in ten, 21 21 17 in one, 23 23 

 17 in one, and 21 26 in one. The gastrosteges vary in num- 

 ber from 149 to 162, males having from 157 to 162, females 

 from 149 to 159; the average in six males is 160.5, in eight 

 females, 154.9. The urosteges vary from 63 to 79, males 

 having from 77 to 79, females from 63 to 67; the average 

 in two males is 78, in four females, 64.7. 



Distribution. This garter-snake ranges north from 

 Mexico into the United States. It has been found in Sono- 

 ra and Arizona, and in California along the Colorado 

 River. It extends its range through Texas to Oklahoma. 

 The details of its distribution through this area are yet to 

 be worked out. As regards Arizona, authentic specimens 

 have been recorded from the vicinity of Tucson and Yuma. 

 At Yuma it occurs on both banks of the Colorado River, and 

 the westernmost limits of its known range are along the 

 banks of this river from Yuma north to Riverside Moun- 

 tain in Riverside County, California. 



We have examined specimens from Fairbank, Cochise 

 County, Tucson, Pima County, Gila Bend, Maricopa Coun- 

 ty, Yuma, Yuma County, Arizona, Colorado River eight 

 miles east from Picacho, Imperial County, California, and 

 Riverside Mountain, Colorado River, Riverside County, 

 California. 



Ruthven examined other specimens with definite locali- 

 ties as follows: Fort Yuma, Imperial County, California; 

 Tucson, Arizona; White Horse Springs and Fort Supply, 



