78 Zoological Society. 
On a New SNAKE FROM THE GALAPAGOS ISLANDS. 
By Dr. ALBERT GUNTHER. 
The genus Herpetodryas, being composed of those Dryadide 
which have the maxillary teeth of equal length and entirely smooth, 
comprises snakes from America and from Madagascar. The follow- 
ing species comes from the Galapagos Islands, and appears to be the 
only Snake as yet known to inhabit that group *. 
HERPETODRYAS BISERIALIS. 
Diagnosis.—Scales in nineteen rows; eight upper labials, three 
posterior oculars. Light brown, with a dark-brown dorsal band, 
serrated on the anterior portion of the trunk, and formed by a double 
series of spots on the middle and on the posterior part of the back. 
A dark-brown streak from the eye across the cheek. Belly irregu- 
larly dotted with brown. 
Hab. In Charles Island (Galapagos). Typical specimen in the 
Collection of the British Museum. 
Description.—The head is rather depressed, flat, and, like the 
trunk and tail, somewhat elongate ; the eye is of moderate size, with 
the pupil round. The rostral does not reach to the upper surface 
of the snout; the anterior frontals are square, the posterior ones 
about twice the size and subquadrangular ; the vertical is rather 
slender, twice as long as broad ; the occipitals triangular and rather 
pointed posteriorly. The nostril is situated between two shields ; 
the loreal nearly square; the anterior ocular extends to the upper 
surface of the head, and is in contact with the vertical. There are 
three posterior oculars, the middle of which is the smallest, the in- 
ferior forming a part of the lower portion of the orbit ; the temporal 
shields are scale-like and rather irregularly arranged. There are 
eight upper labials, the fourth and fifth coming into the orbit. The 
median lower labial is triangular, and of moderate size; ten lower 
labials, the first of which is in contact with its fellow, behind the 
median shield. There are two pairs of elongate skin-shields of equal 
size. The scales are perfectly smooth, in nineteen rows, rhombic, 
those of the outer series being rather larger. Ventral plates 209 ; 
anal bifid ; caudals 108. | 
The ground-colour is a light brownish-grey: a vertebral band, 
formed by dark brown spots, begins from the occiput, and is gra- 
dually lost on the middle of the tail ; it is continuous anteriorly, and 
serrated on both sides, but gradually dissolved into two series of 
brown spots, the spots of each series being confluent on the end of 
* The first mention of a Snake on these islands seems to be in Dampier’s ‘ Voy. 
Round the World,’ ed. 7. vol.i. 8vo. Lond. 1729, p. 103 :—‘‘ There are some Green 
Snakes on these islands; but no other land-animal that I did ever see.” 
Darwin says in his Journ. of Research., p. 381, speaking on the Zoology of 
the Galapagos Islands :—‘‘ There is one snake which is numerous; it is identical. 
as I am informed by M. Bibron, with the Psammophis Temminckii from Chile,” 
Although subsequently, in the ‘ Erpétologie Générale,’ nothing is mentioned by 
Duméril and Bibron about the occurrence of P. Temminckii, or of any other snake, 
in these islands, that determination of Bibron may possibly be correct. If such 
be the case, there are two species of Snakes in that group of islands. 
