MEXICAN SNAKES AND CROCODILIANS — SMITH 419 



head; most dorsal scales with a very narrow black border on their 

 anterodorsal and anteroventral edges. Ventral surface of head with 

 scattered, irregular, bluish stippling not forming distinct marks; 

 dorsal ground color extending to "keel" on each edge of ventrals ; a 

 poorly ^defined light line following the lateroventral "keel"; some 

 bluish stippling medial to this light line, but middle of belly scales 

 immaculate. A small, dark spot at the median corner of each sub- 

 caudal forming a zigzag series of dots down middle of tail. 



Scale rows 17-17-15; ventrals 185; anal divided; tail broken; 

 supralabials 9-9, fourth, fifth, and sixth entering orbit; infralabials 

 11-11 ; preoculars 1-1 ; postoculars 2-2 ; temporals 2-2 ; body length 

 855 mm. 



Variation.— -Ten specimens from the mainland have been examined 

 and are referred to stuarti. They are from Finca Juarez (Nos. 

 110901-6), Salto de Agua (No. 110900), La Esperanza (No. 110899), 

 Acacoyagua (No. 110908), and Colonia Soconusco (No. 110907), all 

 in the vicinity of Escuintla, Chiapas. For reasons noted by Stuart 

 (1941, p. 95) these cannot be considered paratypes of stuarti, although 

 for the time being they are referred to that race in the absence of 

 any apparent morphological differences. 



The entire series of 15 stuarti show a range of variation in ventral 

 counts from 179 to 195. The latter count (from literature) may be 

 in error, as the next highest is 188. Exclusive of this count, the 

 average for 14 specimens is 182.9. One specimen has 10-10 supra- 

 labials, another 9-10; the infralabials are 10-10 in one, 10-11 in one; 

 in one specimen only two labials enter the eye; otherwise the scutel- 

 lation is much as in the holotype. 



Comparisons. — The chief differences between stuarti and slevini 

 are in pattern. In the latter the dark, checkered, anterior ventral 

 pattern is extremely prominent in the young; the marks extend pos- 

 teriorly more than a third the length of the belly. Large adults of 

 the same race still show very distinct, although somewhat more dif- 

 fuse, ventral markings, and they retain a fairly distinct black edging 

 on the dorsal scales. In half -grown specimens, a dark stripe passing 

 through the eye is still evident, while in adults it may disappear. The 

 supralabials are mostly white (cream) in subadults but may become 

 partly suffused with olive in adults. In stuarti the anterior ventral 

 pattern is lost almost completely in adults and subadults ; by this char- 

 acter all except the young can be distinguished at a glance. The black 

 edging on the dorsal scales is so faint that it can be distinguished only 

 by completely exposing the bases of the scales, while in slevini the 

 marks are evident without spreading the scales. The ocular stripe 

 is not apparent, and in adults the supralabial region is entirely pig- 

 mented. 



