SNAKES OF THE GENUS PITUOPHIS 97 



the longer rostral, since in these forms the rostral is as broad as long, 

 except in a few specimens of deserticola where it is slightly longer than 

 broad, although never so long as in sayi. From the forms of the 

 melanoleucus group sayi may be separated by the shorter rostral 

 plate, which is never twice as long as broad in sayi, as it is in the sub- 

 species of melanoleucus, and by the coloration. Thus sayi has a 

 dorsal series of more than 40 dark spots in marked contrast to the 

 light ground color throughout the entire length, and these are more 

 or less uniform in size ; m. melanoleucus has a dorsal series of less than 

 40 black spots on body and tail; m. mugitus is pied brown and white, 

 with the anterior spots usually indistinguishable from the brown 

 ground color, and the total number, when distinguishable, never more 

 than 40; m. lodingi is uniformly black above and slate-gray below, 

 with spots suggested on the posterior part of the dorsum only in 

 young or occasional adult specimens; and m. ruihveni has a dorsal 

 series of 50 chocolate-brown spots on a paler brown ground, with the 

 anterior spots about one-half the size of those in the middle of the 

 body and more or less blended with the ground color, although not 

 indistinguishable. From sayi affinis, s. sayi may be distinguished by 

 the longer rostral, which is nearly twice as long as broad in sayi, and 

 only slightly longer than broad in affinis and by the coloration. In 

 sayi the spots are quadrangular or bar-shaped and are never reddish 

 on the posterior part of the body, wliile in affinis the spots are usually 

 saddle-shaped, at least on the posterior part of the body, and are 

 generally reddish on the posterior part of the body. 



Description. — The body is rather stout, and the snout is rather 

 pointed. The tail is shorter than in other forms of the genus, being 

 0.100 to 0.145 (average 0.122) of the total length. The longest 

 specimen examined was 2,110 mm. in length. 



The dorsal scale formula varies from 25-28-23 to 35-37-27, thus 

 covering almost the entire range of variation for the genus as a whole. 

 The number of scale rows at the neck is 25 to 35, oftenest 29; the 

 maximum number of rows at the middle of the body 28 to 37; the 

 minimum number anterior to the vent 21 to 27. The remaining 

 scutellation is as follows: Ventrals 212 to 244 (average 224.8); caudals 

 46 to 67 (average 56.4); supralabials 7 to 10 (average 8.5), the fourth, 

 fifth, or sixth entering the eye; infralabials 10 to 15, oftenest 12 or 13 

 (average 12.3); preoculars 1 to 3 (average 1.3); postoculars 2 to 5 

 (average 3.4); loreal usually but not always present, occasionally 

 divided to form two plates on one or both sides; one or more azygos 

 plates present in 50 percent of the specimens, usually between the 

 frontal and prefrontals, but occasionally one on either side between 

 prefrontal and preocular, or between postnasal and prefrontal ; rostral 

 nearly twice as long as broad, penetrating from one-third of to all 



