The Opisthoglyph Snakes of North America 



The Genus Trimorphodcni: This is essentially a Central 

 American and Mexican genus. But one species ranges north- 

 ward into the United States. All of the species are of moderate 

 size — some reaching a length of a yard and the thickness of a 

 man's forefinger. The neck is slender, but the head is broad, 

 flat and very distinct, with large eyes, having a cat-like (elliptical) 

 pupil. The species look like viperine, poisonous snakes and their 

 temper is not of the best. The food consists of lizards, young 

 snakes and batrachians — frogs and salamanders. 



THE JEW'S-HARP SNAKE 

 Trimorphodon lyrophanes, (Cope) 



Moderate in size— two and a half to three feet in length. 

 Rather slender; neck very slender; head broad and very distinct 

 — swollen at the temples, and with large eyes, the pupils elliptical. 



Colouration. — Light gray; about twenty pairs of deep brown 

 blotches on the back (to the base of tail) ; tail also blotched. 

 There is an irregular row of blotches on the sides. Abdomen 

 white; dark spots on the edges of many of the shields. 



On the top of the head is a large patch of deep brown, its out- 

 lines suggesting those of a jew's-harp. 



Dimensions. — Total Length 30 inches. 



Length of Fail 6 



Greatest Diameter f " 



Width of Head J " 



Length of Head ij " 



Disiribuiion. — Southern Arizona; Lower California. 



The Genus Sibon: Formation and size similar to the pre- 

 ceding genus, but there is a single loreal plate in place of two as 

 existing with Trimorphodon. Seven species comprise this genus. 

 They inhabit Mexico. and Central America. One extends north- 

 ward into southern Texas. 



THE ANNULATED SNAKE 



Sibon sepienirionalis, (Kennicott) 



Size moderate; body rather slender, the tail gradually 



tapering to a slender tip. Head very broad and distinct from 



neck; swollen at the temples. Eyes large, with elliptical pupil. 



Ventral plate divided — like the preceding species. 



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