41. SONORA 



Description. — Head wide, with flattened top and rather 

 narrow but not greatly depressed snout. Temporal regions 

 not swollen, but head a little wider than neck. Rostral 

 prominent, broad, high, rounded in profile, projecting con- 

 siderably beyond lower jaw, hollowed below, not much re- 

 verted on top of snout, and bounded behind by internasal, 

 nasal and first labial plates. Plates on top of head are a 

 pair of internasals, a pair of prefrontals, a frontal, supra- 

 ocular of each side, and a pair of parietals. Anterior and 

 posterior nasals usually united into a single plate. Loreal 

 often quite small. One preocular. Two postoculars. Tem- 

 porals one followed by two, rarely I + l. Supralabials 

 normally seven, sometimes six, third and fourth reaching 

 eye, sixth largest. Inferior labials six or seven, second 

 small, fourth largest, first pair meeting on median line be- 

 hind the small triagonal mental. Genials in two pairs, the 

 posterior very small. Scales on body smooth, in fifteen rows. 

 Anal plate divided. Gastrosteges in western specimens vary- 

 rng in number from 157 to 183. Urosteges in two series of 

 from 44 to 57. 



The head is pale yellowish brown or orange, with or 

 without a definite or indistinct large dark brown blotch on 

 the parietal and frontal plates. A light vinaceous rufus, 

 pink, or orange band extends along the back from the occi- 

 put to the tip of the tail. This band is about four or five 

 scales wide on the body, and two or three on the tail. The 

 scales of the central two or three rows usually show only 

 very faint darker markings, but those of the more lateral 

 rows are marked each with a central dash of dark hair brown, 

 while their margins are whitish. These dark dashes there- 

 fore appear as a brown line along the middle of each row 

 of scales, with the exception of a few of the dorsal rows, 

 while the ground color is reddish or pink dorsally and white 

 laterally. The reddish dorsal band may be rendered less 



