82 CROTALUSDURISSUS. 



quadrilateral and excavated behind, the posterior is lunated in front to complete the 

 nostril. The superior orbital plates are regularly oval, the greatest extent of the 

 oval being in the antero-posterior direction; their outer margin forms a strongly 

 marked projection over the eye. There are thirteen labial plates to the upper 

 jaw; those in front larger and quadrilateral, the posterior smaller and rhomboidal; 

 above the labial plates is a row of small scales or plates, continuous with the 

 inferior orbital. The anterior orbital is quadrilateral and very long; the posterior 

 is of the same form, but only half the size. There are four small inferior orbital 

 plates, which complete the lower walls of the orbit. Above the labial range is a 

 row of small scales that form the lower walls of a deep pit, completed above by a 

 large lunated plate; this pit is situated midway between the nostril and the eye, 

 but on a lower plane. The nostrils are large, and very near the snout, but open 

 laterally. The eyes are large, and extremely brilliant when the animal is enraged; 

 the pupil is dark, oval and vertical; the iris flame colour. The mouth is large, the 

 jaws strong, the upper furnished with poisonous fangs. The neck is very much 

 contracted, and covered with carinated scales, larger than those on the head. 

 The body is elongated, but thick, and covered with rough carinated rhomboidal 

 scales above, and broad plates below. The tail is short, slightly conical, and 

 sustains a greater or less number of rattles. 



Colour. The superior surface of the head is ash colour, with a brownish band 

 passing from the eye to the commissure of the mouth. The neck and body are 

 pale ash colour, with a vertebral line of yellow, including three scales; behind the 

 occiput on each side of this line is an oblong dark spot. The body is marked 

 with a triple series of dark irregular blotches and bars along the back. In front 

 the blotches of the vertebral series are oblong transversely, widely emarginate 

 before and behind; they vary, however, in shape, near the middle of the body; 

 they resemble chevrons, with an acute angle towards the head; beneath the termi- 

 nations of these spots on the flanks is a row of subquadrate dark spots; near the 

 tail the vertebral and lateral series unite to form a band, and between these there 

 is another row of obsolete gray spots. The abdomen is dirty reddish-straw 

 colour, freckled with minute black dots. 



