Crotalus helleri, known as the Southern Pacific rattlesnake, black diamond rattlesnake, and by other names, is a pit viper subspecies found in southwestern California and south into Baja California, Mexico, that is known for its regional variety of dangerous venom types. Adults are 24–55 inches (61–139 cm) in length. The color pattern consists of a pale brown, gray-brown, or yellowish brown ground color overlaid with a series of large, dark brown dorsal blotches that may or may not have pale centers. The blotches are more diamond shaped, as opposed to those of C. o. oreganus that are more hexagonal, and are bordered by light scales. The tail rings are not clearly defined. In juveniles, the end of the tail is bright orange, but this turns to brown as the snakes mature. In adults, the base of the tail and the first segment of the rattle are brown. The postocular stripe is moderately to very clearly defined. In juveniles, this stripe is bordered above by a pale stripe, but as the snakes mature this turns to drab yellow or brown. A conspicuous pale crossbar is sometimes present across the supraoculars, after which the head is a uniform dark color. In some older snakes the head is mostly dark with almost no trace of the supraorbital crossbar, or none at all. (Source: Wikipedia.org, CC BY-SA)