21 



CROTALUS OREGONUS.—HolbrooL 



Plate III. 



Characters. Head very large, triangular, truncated anteriorly; covered above 

 with plates, and with scales on the vertex and occiput; upper jaw armed Avith 

 fangs; a broad white bar between the orbits, and two others on the side of the 

 head; one begins above the pit, the other below, and are confluent behind the 

 angle of the mouth; body thick, and marked above with two zigzag white lines, 

 that form a series of trapezoidal or sub-triangular dusky spots, with white 

 margins.— PI. 177. Caud. PI. 22. Rattles, 3. 



Description. The head is very large, triangular, broad behind, narrow and 

 truncated, or slightly rounded in front, and is proportionably longer than in other 

 Rattlesnakes; above it is covered with plates anteriorly, and with scales on the 

 vertex and occiput; the rostral plate is large and triangular, Avith its apex slightly 

 truncate and turned upwards; the nasal plates are two in number, the anterior is 

 quadrilateral and very large; the posterior semilunar and smaller, with a concavity 

 in front for the nostrils; the superior orbital plate is large, irregularly quadri- 

 lateral, and projects over the eye; there are two anterior orbital, nearly 

 quadrilateral, and two posterior orbital plates, nearly of the same size and form, 

 with three inferior, oblong and narrow. In front of the anterior orbital plate, 

 and above the labial range, are several small scales, making the posterior and 

 inferior walls of the deep pit between the eye and the nostril, which is completed 

 above and in front by two large plates. 



