A large (up to 1,219 mm or 48" in total length excluding rattle), brown, gray, yellow-brown, or golden yellow rattlesnake with a series of large, black or brown, blotches on the back (dorsal blotches). The blotches appear jagged-edged because each of this snakes dorsal scales is usually but a single color. A few light patches mark the interior of each dorsal blotch. The blotches are hexagonal with thin "straps" trailing down the sides to the belly. On the posterior part of the body the blotches become narrow, muted crossbands. The tail is black, sometimes with muted, dark, gray-brown rings. The top of the snout is usually black or dark brown. The pupils are vertically elliptical and the dorsal scales are keeled. The neck is slender and the head is broad and triangular. On the end of the tail is a rattle composed of a series of loosely interlocking keratinous sections. A new section is added each time the snake sheds its skin.