HERPETOLOGY OF ZITNI MOUNTAINS — GEHLBACH 305 



are thus allocated with D. p. regalis, which is best distinguished by the 

 large, sexually dimorphic number of ventrals. Thirty- three females 

 have 220-247 (x 233.9±1.3) ventrals, while 28 males have 204-229 

 (217. 3± 1.2). Over a range of 43 ventrals there is only a nine-scale 

 overlap between the sexes. On the other hand, 25 males have more 

 subcaudals (62-81, x 70.9 ±0.98) than 28 females (55-73, 64.8 ±0.73). 

 Here the overlap, 11 scales in a range of 26, is relatively greater, 

 rendering number of subcaudals inferior to number of ventrals as an 

 external criterion of sex. Equally striking sexual dimorphism obtains 

 in D. p. arnyi and D. p. dugesi, which have fewer ventrals than D. p. 

 regalis (fig. 10). 



A single ringneck from southern Chihuahua (BYU 14243) has only 

 196 ventrals, suggesting intergradation with D. p. dugesi (Tanner and 

 Robison, 1960, p. 68). It further resembles D. p. dugesi in number of 

 dorsal scale rows (17-17) and the coloration described above. A 

 specimen from Durango is likewdse intermediate in ventral count 

 and color (see above and fig. 10) but is closest to D. p. regalis horn 

 Chihuahua in number of dorsals (17-15) and temporals (1-1). Un- 

 fortunately, the other Durango specimen (UMMZ 102527) is in such 

 poor condition that exact analysis of its scutellation is impossible. 

 The Durango ringnecks and the above-mentioned individual from 

 Chihuahua are considered intergrades since they bridge the previous 

 morphologic and geographic gap between D. p. regalis in Chihuahua 

 and D. p. dugesi in Nayarit. 



Martin and Harrell (1957, p. 469) listed D. punctatus among 

 vertebrates that may have dispersed between the eastern United 

 States and Mexico. The relationship of D. p. dugesi to D. p. arnyi 

 through intergradation with D. p. regalis implies that dispersal via 

 the Sierra Madre Occidental and the montane Southwest deserves 

 equal consideration. Lower ventral and subcandal scale counts in 

 D. p. dugesi and D. p. arnyi could be considered convergence in view 

 of the distributional hiatus in northeastern Mexico. This hiatus 

 may not be real, however, because a specimen described by Blanchard 

 (1942, p. 59) from San Luis Potosi, Mexico, appears to be somewhat 

 intermediate between D. p. arnyi and D. p. regalis and indicates that 

 other such individuals occur in the region and possibly to the north 

 also. Blanchard (1942, pp. 129-132) described breaks in range, 

 considered by him important in maintaining D. p. regalis and D. p. 

 dugesi as distinct species, that recently have been filled in. 



The secretive nature of Diadophis can be cited as a reason for its 

 seeming rarity in the Southwest and Mexico. In the Zunis, a male 

 collected August 17, 1959, was crawling over sandstone rubble near 

 a small stream at 9:45 a.m. Although the locality, in pinyon- 

 juniper-ponderosa ecotone at 7200 feet, had been worked intensely 



