CERASTES AND ECHIS. 85 
colder part of the year. It is, therefore, only in the hottest summer 
months that the traveller is exposed to the danger of being bitten.” 
Dr. Gray refers doubtfully to this genus both the 2chidna inornata 
(Fig. 21) of Sir A. Smith, and the Z. maurittanica of Duméril ard 
Bibron, from Algeria; likewise a Peruvian species named Zchidna 
ocellata by Tschudi, which is the only known instance of a member 
of this family inhabiting the New World. The appellation Zchidna, 
however, belongs properly to the Porcupine Ant-eaters, of the class 
Mammalia. 
The species of Cerastes and of Echis have the nostrils much 
smaller than the preceding, and are Vipers of less formidable size. 
In the two species of Cerastes, or Horned Viper, the eyebrows of 
the male bear commonly a sort of horn. C. Hasselguistit is com- 
mon in Egypt; and the other, C. RzcAzz, inhabits Tripoli. Of Zchis 
there is one species in Egypt and North Africa, 2. arenicola; and 
another in India, £. carinata. ‘The lattér grows to about twenty 
inches long, of which the tail measures two inches and a third. 
These Vipers commoniy lie half-buried in the sand, which they much 
resemble in colour. They feed upon Centipedes (Scolopendra), and 
no case is known of their bite having proved fatal. 
The remaining Vzpertde@ have the head more or less shielded. 
They are divided by Dr. Gray into Vigera (with two European 
species, not found in Britain—V. asfzs from the Alps, and V. 
ammodytes from the countries bordering on the Mediterranean) ; 
Pelias, which contains only the common British Adder, P. derus ; 
Sepedon, with one species only, from South Africa, S. Aemachates ; 
Causus, with also only one African species, C. rhombeatus; and 
finally Acanthopis, founded on the Death Adder of the Australian 
colonists, A. antarctica, which is the only member of. the family 
Viperide known to inhabit Australia, where the poisonous Colubrine 
Snakes are so numerous. It is also the only known species the 
scales of which are smooth or not keeled. It seldom exceeds thirty 
inches in length, and varies a good deal in colour. Like other 
Viperide, it is sluggish in its movements, but when irritated it flattens 
itself out generally in the form of the letter S, turning round to one 
side or the other with astonishing rapidity, but never jumping at its 
enemy or throwing itself backward, as the Puff Adders are described 
to do. The Death Adder is found in almost every part of Australia 
northward of the thirty-sixth parallel of south latitude. | 
The Common Adder (Peééias berus, Fig. 22), is not improbably 
the "Ex:s of Aristotle, and the Vipera of Virgil, as it is the AZanasso 
of the Italians, the Adder of the country-people in England and 
