Total length, 825 millimetres; tail 145.
Habitat: Guatemala.
(c) Sistrurus.
Head very distinct from neck, covered above with nine large symmetrical shields; eyes rather small, with vertical pupils. Body cylindrical; scales keeled, with apical pits; tail short, ending in a segmented horny apparatus (rattle), producing a special sound; subcaudals all or the majority in a single row.
(1) S. miliarius (Ground Rattle-Snake).—9-11 supralabials; scales in 21 or 23 rows, strongly keeled; 127-139 ventrals; 27-36 subcaudals; rattle short, consisting at the most of 10 segments.
Colour greyish, yellowish, or brown, the vertebral line often orange; two undulating dark stripes from between the eyes to the occiput, the enclosed space usually orange; belly whitish, spotted with dark brown or black.
Total length, 520 millimetres; tail 70.
Habitat: South-eastern North America, from North Carolina to Texas.
(2) S. catenatus (Prairie Rattle-Snake, or Massasanga, [fig. 71]).—Two or three series of scales between the eye and the labials; 11-14 supralabials; scales in 23 or 25 rows; 136-153 ventrals; 20-31 subcaudals.
Colour the same as in S. miliarius: a dark spot on the parietal shields.