CHAPTER XXXI: THE FLAT-NOSED SNAKES 



Genera Salvadora and Phyllorhynchus 

 Unique Serpents of the Southwestern United States and Mexico 



From all other North American snakes, the reptiles of the 

 genera Salvadora and Phyllorhynchus may be distinguished by 

 the peculiar development of the shield on the snout — the ros- 

 tral. This is wedge-shaped, the flat portion forward, and with 

 sharp, projecting edges. The unusual formation of the rostral 

 gives the head a blunt, square outline. With Salvadora, the 

 development is moderate, though at once distinct; with Phyl- 

 lorhynchus however, the formation of the rostral is carried to 

 such an extreme that the two species are extremely grotesque 

 and appear as if they had a curved shield loosely attached to 

 the front of the snout. 



The Flat-nosed Snakes are of moderate size; they occur 

 in the southwestern United States and in Mexico. 



Key to the North American Species 



A. Pupil of eye round. Nose plate {rostral) moderately de- 

 veloped in the form of a projecting shield, curved back 

 over the top of the snout. Genus Salvadora 



Yellow, with brown bands (lengthwise). 



Graham's flat-nosed snhKE, S. grahamice. 

 Distribution. — Western Texas to Lower California. 



B. Pupil elliptical. Rostral plate greatly developed in the 

 form of a projecting shield. Genus Phyllorhynchus. 



a. Scales keeled on latter portion of body. 

 Whitish; about fifteen brown cross-bands. 



brown's flat-nosed snake, p. browni. 

 Distribution. — Southern Arizona. 



b. Scales smooth. 



Whitish; about thirty blotches on back. 



peninsula flat-nosed snake, p. decurtatus. 

 Distribution. — Lower California; southwestern Ari- 

 zona. 



291 



