CHECKLIST OF THE SNAKES OF MEXICO 127 



Pattern tricolor, with black, grayish, and reddish cross bands on body 

 or tail or both, or the reddish may cover most of body and tail, in 

 which case black and grayish bands persist only on nuchal region ; 

 nasal plates sutured below, nostril in most specimens, but frequently 

 entire ; color pattern with marked sexual variations ; scale rows 

 15-15 {michoacanensis group) 2 



2. Tail reddish, unbaiided michoacanensis michoacanensia 



Tail with triads of black, grayish, and reddish bands 3 



3. Unsplit black bands much longer (anteroposteriorly) than grayish 



bauds, or else all black bands split by red ; at least some of anterior 



body bands always split by red michoacanensis mutabilis 



Unsplit black bands approximately equal in length to grayish bands ; in 

 single known specimen (female) none of body bands split by 

 red aequalis 



4. Anterior scale rows 15, rarely 14 or 16; temporals generally 1-2 (1-2 



or higher on both sides in 96 percent of specimens) 5 



Scale rows 13-13, rarely 14-13 or 14-14; temporals generally 1-1 (1-1 

 on one or both sides in 87 percent of specimens) ; color brownish, 

 unhanded ; ventrals of males 126 to 142, of females 13G to 151 taylori 



5. Caudals 53 or more in males, 45 or more in females ; scale rows 15-14 



(posterior scale rows counted in reference to scale reduction in mid- 

 dorsal region, disregarding lateral irregularities) 6 



Caudals 52 or fewer in males, 44 or fewer in females ; scale rows 

 various 8 



6. Ventrals minus caudals 97 or fewer in males, 115 or fewer in females ; 



tail 23 to 25.2 percent of total length in males, 20.3 to 21.6 percent 



in females (in preserved specimens) semiannulata blanchardi 



Ventrals minus caudals 98 or more in males, 116 or more in females ; 

 tail 19.4 to 23.3 percent of total length in males, 16.4 to 20 percent 

 in females 7 



7. Without cross bands, but with a distinct, rather sharp-edged dorsal 



reddish stripe that contrasts in color with the bluish-gray to 



brownish-gray sides semiannulata linearis 



With or without cross bands, but if bands are lacking, color not as 

 described above 10 



8. Ventrals minus caudals in males generally more than 109, in females 



presumably averaging over 127 (no females known) ; scale rows 15-14; 



pattern consisting of dark cross bands semiannulata semiannulata 



Ventrals minus caudals in males generally less than 109, in females 

 generally less than 127 ; scale rows and color as above or other- 

 wise 9 



9. Scale rows typically 15-15, occasionally 15-14 ; ventrals plus caudals in 



males 195 or less in 82 percent of specimens (average, 191.1), in 

 females 200 or less in 92 percent of specimens (average 194.4) ; 



color highly variable episcopa 



Scale rows 15-14-13 in the four known males and 15-14 in the single 

 known female; ventrals plus caudals in 3 males 196 to 200 (average, 



198.6), in the female 203; color unhanded, all brown mosaueri 



10. Ground color yellow-brown ; cross bands relatively wider, closer to- 

 gether, not tapering laterally bancroftae 



Ground color white, generally suffused with cream or red in life ; cross 

 bands narrower, farther apart, tapering laterally semiannulata isozona 



