VARIATIONS OF GAKTER-SNAKES. 



163 



series in which males and feniales are re})resente(l in about equal pro- 

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

 tail length, .23; but much laro;er 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 



19-17^ 

 13-11-15 

 n-19-n-15 



Guatemala, Valley of Uuana- ■ Durangd, Fort Ilu- San Ilde- Davis Helotes, 

 Cent. Ainer. Mexico, juato, Mexico. aehuca, fonso. Mts., Texas. 



Hex. Zacaulti- Arizona. NewMex- Texas. 



pan, ico. 

 Mexico. 



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 (ISSO, 22-23) has described these as a distinct variety 

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

 This pattern is foimd in occasional specimens from nearly every 



10 



9 

 8 



Guatemala, Valley of Guana- Durango, Fort Hu- San Ilde- i)avis Mts., Helotes, 



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



Mex. Zacaulti- Arizona. New Mcx- 



pan, ico. 



Mexico. 



Fig. 72.— Diagram showing the variation in the number of supralabials in Thamnophis eque.s. 



locality in the range of eques, and while of more frequent occurrence 

 in the northern j)art 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 tlii-ee are 

 typical, eq^ues, and the others, while agreeing with them in scutella- 

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



