124 VENOMS 
segments fall off and are at once replaced Contrary to the belief 
which was long entertained, their number bears no relation to the 
age of the snake. 
Rattle-Snakes are met with especially in stony and arid 
localities, or among brushwood near water. They hardly ever bite 
except when surprised or attacked. 
(1) C. terrificus (Dog-faced Rattle-Snake, Cascavella in Brazil; 
fig. 73).—Snout very short; three or four series of scales between 
the eye and the supralabial shields ; body-scales in 23—31 rows, 
dorsals very strongly keeled; 160—199 ventrals ; 18—30 sub- 
caudals. 
Colour brown, with a series of darker, light-edged rhombs, 
often lighter in the centre; a dark streak from the eye to the 
angle of the mouth ; belly yellowish-white, uniform or spotted with 
brown ; tail generally brown or blackish. 
Total length, 1,820 millimetres ; tail 130. 
Habitat : Arizona, New Mexico, and Texas to Southern Brazil, 
and Northern Argentina. 
(2) C. scutulatus (Texas Rattle-Snake ; fig. 74).—13—16 supra- 
labials; scales in 25 or 27 rows; dorsals striated and strongly 
keeled ; 167—170 ventrals ; 18—20 subcaudals. 
Colour yellowish or greyish-brown, with a series of large dark 
brown light-edged rhomboidal spots ; an oblique dark streak below 
the eye; belly uniform yellowish-white. 
Total length, 760 millimetres ; tail 65. 
Habitat: Arizona, New Mexico, Texas, North Mexico. 
(3) C. confluentus (Pacific or Mottled Rattle-Snake; fig. 75). 
—Upper head-scales small, striated; 13—18 supralabials; body 
scales in 25—29 rows, striated and strongly keeled; 168—197 
ventrals ; 17—34 subcaudals. 
Colour yellowish, greyish, or pale brown, with a dorsal series 
of large brown or red spots, usually rhomboidal or transversely 
elliptic in shape; a light streak or triangular marking across the 
supraocular shields; belly yellowish, uniform or spotted with 
brown. 
