82 . 
ON THE PHYSIOGNOMY OF SEEPENTS. 
see in the serpents properly named venomous, and in some 
others. These pronounced features, however, do not 
always constitute the distinctive characters of dangerous 
Ophidians ; for many innocuous species, such as the genera 
Heterodon, Homalopsis, Boa, and some others, join to a 
farouche physiognomy, a natural gentleness ; while the 
Elaps, the Naja, and the Bungarus, which are not distin- 
guishable hy exterior signs from the Colubri, are provided 
with the same redoubtable weapons as the Viper and the 
Crotalus. 
The Neck of Ophidians has often the same shape as their 
trunk ; and it is only in the Naja and in some Xenodons 
that the ribs, more straight than usual, and capable of a 
considerable horizontal movement, give a more flattened 
form to the neck. It must be remarked, however, that 
most serpents have the faculty of flattening and enlarging 
the neck, as is observed when they are enraged, and utter 
those hissings which usually are the prelude to an attack. 
THE COLOUKS. 
It is not possible to lay down fixed principles on the 
system of colours in Ophidians. Sometimes uniform and 
dull, sometimes shining with a brilliancy equal to that of 
precious stones, their tints are infinitely varied, and very 
difierently disposed, not only in the various races, but often 
also in species of the same genus. In others, on the con- 
trary, we observe in allied species a certain uniformity in 
the distribution of the colours, which are often analogous 
to the surrounding objects in the places inhabited by these 
animals. Many climbing serpents, for example, present a 
livery of uniform green, absolutely resembling that of the 
leaves ; while others, as many species of Dendrophis and 
Dryiophis, in this respect resemble small naked branches ; 
and, lastly, in the Dipsas, the system of colouring simulates 
the old stem of a tree covered with fine and luxuriant 
mosses. The serpents which frequent fresh water are 
generally remarked for their sombre and uniform tints ; 
the green, the yellow, and the blue colours which ornament 
the bodies of sea-serpents confound them with the waves 
