238 OPHIDIA. 



Total lengtb, 17 inches to 2 feet. 



Prefers hilly and dry places exposed to the rays of the 

 sun ; feeds on mice, frogs, and other small animals, and is 

 itself often devoured by birds of prey. The varieties of 

 colour are as numerous, and of the same kind, as in V. 

 asj^is ; the tip of the tail, however, is said to be always of 

 a red iron-brown tinge. 



Inhabits Austria, near Vienna, and elsewhere, Hungary, 

 Carniola, Istria, Dalmatia, and the North of Italy, especially 

 near Ferrara ; is found in Greece, and was the only Viper 

 obtained in the Morea by the French Scientific Expedition . 



Genus TRIGONOCEPHALUS. 



Provided with spurious nostrils, or nasal pits between 

 the eye and the true nostril ; tail with a sharp point ; top 

 of the head always covered with plates, of which the central 

 is largest ; the scales of the head and back keeled. Re- 

 sembles the Rattlesnakes in general appearance. 



Trigonocephalus Halys. 



Trigonocephalus Halys, Dum. et Bib. vol. vii. p. 1495. 

 Coluber Halys, Pallas, Zoog. Ross. As. vol. iii. p. 49. 



Description. — Plates on the head nine in number, the two 

 first very small, rounded in front, resting on the two 

 frontals ; the central plate uneven, surciliary plates wide, 

 parietals long, narrowed behind ; ventral plates, from 162 

 to 170 ; subcaudal, about forty pairs. Upper parts pale 

 grey, with transverse marks of olive-brown; sometimes 

 the spots on the back are united to each other ; on the neck 

 is a mark in the shape of a horseshoe, prolonged, open 

 behind, preceded by two other elongated marks beginning 

 upon the parietal plates. In some specimens the colour of 

 the back is greenish, with crossed and transverse white lines. 



