S2 ON TUE niYSIOGNOMY OF SERPENTS. 



sec 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, Ilomalopsis, Boa, and some others, join to a 

 farouche physiognomy, a natural gentleness ; while the 

 Elaps, the Naja, and the Buiigarus, which are not distin- 

 guishable by exterior signs from the Colul:>ri, 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 COLOURS. 



It is not possible to lay down fixed principles on the 

 system of colours in Ophidians. Sometimes unifonn and 

 dull, sometimes shining with a brilliancy equal to that of 

 precious stones, their tints arc infinitely varied, and very 

 differently 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 gi-een, 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 



