VAEIATIONS OP GARTER-SNAKES. 121 



bordered with darker. Belly greenish or bluish ash, marked with 

 numerous small black spots, and a bar at the base of each ventral, 

 which is usually prolonged outward to form a more or less irregular 

 median ventral band. Throat yellow. 



Habits and habitat relations. — Little data is available on the nabitat 

 relations of tliis snake, but it is undoubtedly particularly aquatic in 

 its habits. Thus, Cope (1883b) states of the wSan Francisco River 

 specimen obtained by him: 



The only specimen of this species which I have seen living was taken in a seine 

 net with which I was fishing near the bank of the San Francisco River. It dove into 

 the net, seeking the bottom of the water as a place of concealment, as is the habit of 

 E melanogaster and contrary to that of E. sawrita and E. macrostcmma, which swim 

 preferably on the surface, seeking concealment under banks. 



Range. — As at present known, this form is confined to the northern 

 part of the Mexican plateau (above northern Durango) and thepropla- 

 teau region in southwestern New Mexico and southeastern Arizona (fig. 

 52). The conditions of this habitat have already been described 

 (p. 46). Specimens have been examined from Chihuahua and San 

 Andreas, Chihuahua; Parras, Coahuila, and Coyotes, Durango, but it 

 occurs also in southern Arizona, as Cope (1883b, 1300-1301) records 

 a specimen from the San Francisco River in southern New Mexico, 

 and the type of rufopunctatum came from "southern Arizona." 



Variation. — Very few facts are available for the study of variation 

 in this form. The dorsal scale rows are very constantly 21-19-17. 

 A single specimen from San Andreas, Chihuahua, has 21-23-21-19-17, 

 and another from Chihuahua, Chihuahua, has 19-21-19-17. No 

 geographic variation is discernible in this character in the material 

 at hand, the more northern and southern specimens all having gen- 

 erally 21-19-17 rows. The same thing is true of the labial scutes, 

 the formula being 8/ 10 or 8/11, or 9/ 10 or 9/11, but with no certain 

 differences in those from different localities, although only those 

 from Chihuahua have 9 in the superior series. 



In regard to the ocular scales the conditions are somewhat differ- 

 ent. In all of the specimens examined from the vicinity of Chihuahua, 

 Chihuahua, there are three preoculars and three or four postoculars, 

 and the eye is excluded from the posterior subocular labial by the 

 lower postocular, but in those from northern Durango and southern 

 Coahuila the formula is 2-3 or 1-3 and the eye is fairly in contact 

 with two labials. Similarly the type of rufopunctatum from "southern 

 Arizona" is said to have had one preocular on one side and two on 

 the other, as well as three and four postoculars, with the eye in con- 

 tact with two labials. But little idea can be obtained as to the 

 range or mean in the variations of the ventral and subcaudal scutes. 

 In the material examined the males have in general 162-166 ventrals 

 and 73-83 subcaudals, the females 153-159 ventrals and 64-69 sub- 



