Adults are short and exceedingly stout, commonly growing to 18–24 inches (46–61 centimetres) in total length.

[3] At midbody there are 23–27 rows of dorsal scales that are strongly keeled, tubercular in large specimens.

[3] These snakes have sometimes been mistaken for young bushmasters (Lachesis muta), but can easily be identified by their lack of a specialized tail tip.

[3] Found in eastern Mexico from San Luis Potosí southeastward on the Atlantic versant and lowlands.

The type originally lacked locality information, but apparently "Mexico" was filled in some time later.