406 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.48. 



Palisade, Nevada, at a lower altitude (4845 feet) are larger and 

 have an increased number of dorsal scales. Ruthven (1908), in his 

 admirable paper, Variations and Genetic Relationships of the Garter- 

 Snakes, has shown quite conclusively the northward dwarfing of the 

 species in the genus Thamnopliis, both in regard to scale characters 

 and size of body. It would appear that this latitudinal variation 

 is not restricted to any one genus or family of American reptiles, but 

 occurs alike in both the saurians and the serpents. Whether the 

 altitudinal variations are as widespread or as marked must be decided 

 by future studies. 



It is not within the scope of this work to consider the factors which 

 have caused the variations indicated. That is a problemfor the experi- 

 mentalist. Undoubtedly important results await the student who 

 will test the inheritance of squamation and size under artifici al environ- 

 ments in which the temperature, humidity, and food supply can be 

 controlled. 



CROTAPHYTUS COLLARIS BAILEYI (Stejneger). 



Locality. — Six specimens of this form were taken near the Pyramid 

 Lake Indian Agency, and four at Derby, Nevada. There is also a 

 male in the Stanford University collection from the Palmetto Moun- 

 tains, Esmeralda County, Nevada. It has been previously recorded 

 in the Lahontan Basin at Big Creek Ranch, Pine Forest Mountains, 

 and from the Truckee River, Nevada. 



Status and variation. — The above-mentioned specimens have two 

 rows of interocular scales and small supraoculars, characteristic of 

 this subspecies, an average of 11 rows of the latter across the greatest 

 width of the supraocular region. Concerning the interocular scales, 

 it might be well to state that there are in the Stanford University 

 collection two specimens, a male from Bisbee, Cochise County, Arizona, 

 and a female from Cedar Ranch, Colorado Canyon, Arizona, each of 

 which has a single-fused interocular. Meek (1905, p. 8) mentions a 

 specimen from Winslow, Arizona, showing a like variation, and it 

 would seem that such variants were of quite frequent occurrence in 

 this region. All the Nevada and California individuals which I 

 have seen, however, have a double series of interoculars. 



The average number of femoral pores in 10 individuals is 17, the 

 extremes 15 and 19. 



The six males in the series have the anterior part of the double black 

 collar continuous ventrally and a black patch on either side of the belly 

 extending from the middle of the trunk across the inguinal region 

 to a point one-third the distance down the posterior surface of the 

 thigh. A single specimen from Esmeralda County, Nevada, and three 

 others from Lytle Creek, San Bernardino County, California, in the 

 Stanford University collection, are of this same type of coloration. 

 The specimens from Arizona and New Mexico, which were compared 



