CROTALUS. 



3. CrotalUS atrox, B. & G. — Head subtriangular. Plates on head ; 

 2 anterior frontals in contact, between these and superciliaries, on side of 

 the crown, 2 imbricated plates. Space enclosed occupied by smaller scales. 

 Superciliaries bordered by a row of larger scales; the anterior much largest. 

 Three rows of scales between labials and suborbitals. Labials 16 above; 

 1st, 5th, and 7th largest; — 15 below, 1st and 3d largest. Dorsal rows 

 25-27: 2 exterior rows smooth. On the tail 3-6 half rings. Color yel- 

 lowish brown, with a continuous succession of dorsal lozenges, sometimes 

 truncate before and behind; intervals all narrow. A single transverse 

 light line on superciliary. Stripe from superciliary directly to the angle 

 of the mouth. 



General style of coloration somewhat as in C. adamanteris. Ground- 

 color above dull yellowish brown, with a series of subhexagonal 

 patches from the head nearly to the tail, in an uninterrupted series, 

 separated throughout by narrow lines. "We may refer the markings 

 to the intersection of two series of light yellowish lines, about 40 in 

 number, crossing obliquely from each side across to the other, along 

 the anterior half of as many oblique series of scales. The lateral de- 

 cussation is along the sixth row of dorsal scales; on the back, where 

 they cross, the lines are confluent for a breadth of five or sis scales, 

 making a series of transverse lines across the back, truncating the 

 obtuse angles of the rhomboids, which would otherwise be produced. 

 Sometimes the acute lateral angle of the rhomboids are also trun- 

 cated. Laterally, the yellowish lines are more or less obsolete, leav- 

 ing a more or less distinct chain pattern. The rhomboids or sub- 

 rhomboids enclosed have a narrow margin of dark brown, lighter 

 toward the centre. In all cases the interval between the successive 

 rhomboids is but one or two half scales in width. The lateral rhom- 

 boids and triangles referred to in C. adamanteus are indicated by 

 two alternating series of dark brown blotches, the first along the 3d 

 and 4th lateral row, opposite the apices of the rhomboids ; the second 

 along the Gth and 7th, and alternating with the same; the spots 

 occupy one scale, or part of four contiguous ones. Space between 

 these rhomboids and the yellowish lines, dull yellowish brown. Be- 

 neath nearly uniform yellowish, slightly clouded on the sides of the 

 scales. On the tail the blotches are confluent into 3 or 6 dark brown 

 half rings, interrupted on the under surface. General distribution 

 of lines on the head much as in C. adamanteus ; a narrow light line 

 from the posterior end of the superciliary backward, directly to the 



