VARIATIONS OF GAETER-SNAKES. 



163 



series in which males and females are represented in about equal pro- 

 portions are about as follows: Ventrals, 160-170; subcaudals, 75-85; 

 tail length, .23; but much larger series are necessary to properly 

 define these characters. 



As in the case of scutellation, there is little marked variation in 

 the coloration. However, the specimens in which the dorsal spots 



19-n 



19-11-15 



n-i9-n-i5 



Guutciiiala, Valley of Guana- 

 Cent. Amer. Mexico, juato, 

 Mex. Zacaulti- 



pan, 

 Mexico. 



Durango, FortHu- Sanllde- Davis Ilelotes, 



Mexico. achuca, fonso, Mts., Texas. 



Arizona. New Mex- Texas, 

 ico. 



Fig. 71.— Diagram showing the variation in the dorsal scale formula in Thamnophis eques. 



tend to become distinct on the scales and fused into cross-bars ante- 

 riorly (see p. 159) are principally from the southern part of the United 

 States. Cope (1880, 22-23) has described these as a distinct variety 

 ocellata (and Jan has made them the basis of the species collaris). 

 This pattern is found in occasional specimens from nearly every 



10 



9 



8 



*4 



3 / 

 ) / 

 ,/ 



-<<\ 



<) 



9\ 



Guatemala, Valley of Guana- Durango, Fort Hu- San Ilde- Davis Mts., Ilelotes, 



Cent. Amer. Mexico, juato, Mexico. achuca, fonso, Texas. Texas. 



Mex. Zacaulti- Arizona. New Mex- 



pan, ico. 



Mexico. 



Fig. 72.— Dia'gram showing the variation in the number of supralabials in Thamnophis eques. 



locality in the range of eques, and wliile of more fref[uent occurrence 

 in the northern part still occurs only as an individual variation of the 

 normal coloration. In regard to the loss of the stripes, the case is 

 somewhat different. Thus, in the series in the U. S. National Museum 

 from Zacaultipan, Hidalgo, Mexico, out of six specimens tlu^ee are 

 typical, eques, and the others, while agreeing with them in scutella- 

 tion, differ in the apparent total absence of lateral and dorsal stripes. 



