Locally fairly common. Two named subspecies occur, mainly in the arid and shore zones: Galapagos Snake dorsalis (Baltra, Rabida, Santa Cruz, Santa Fe and Santiago), Fernandina Snake occidentalis (Fernandina) and Isabela Snake helleri (Isabel a and Tortuga). Feeds by constricting its prey, although slightly venomous.
Virtually impossible to identify unless examined in the hand, identification being confirmed on the basis of the shape, pattern and number of scales on certain parts of the body. As in the other species, predominantly brown with yellow stripes or dark grey with yellow spots on their upper-side forming a zigzag pattern. However, the present species only occurs on islands from which P. biserialis is absent, and although present on the same islands as A. slevini, that species is considerably smaller.