22 
ON THE PHYSIOGNOMY OE SEEPENTS. 
performed in the Saurians by the general form and organs 
of locomotion, are wholly subordinate to their general 
organization.^ It is thus evident that the characters 
formed on these parts, must always lead to an artificial 
system ; and it is equally clear, from what we shall state, 
that the two types on which Saurians and Ophidians are 
modelled, are connected by numerous intermediate forms. 
Hence many naturalists have refused to adopt the two 
foregoing divisions, which they have combined into one 
whole. This mode of viewing the question is equally 
susceptible of defence or attack; and it is not out of 
deference to any system that I propose to follow either 
view. However, as I propose to treat in my book of ser- 
pents properly so called, it is necessary to give a definition 
of the beings I mean to include in this category. It is 
easy to conceive the idea of a serpent, when we take for 
the type one of the species in which all the characters of 
the order are united ; but it is difiicult to assign the dis- 
tinctive marks which separate, in a precise manner, the 
Ophidians from the Saurians. 
The characteristics of the animals we denominate Ser- 
pents, appear to me to consist in a very elongated body, 
furnished with a tail, and covered by a defensive armour 
of hard scales, which moves, supported on its ribs, by 
means of lateral undulations, which has a form concen- 
trated, in its transverse dimensions, into the smallest 
* A comparative examination of specimens has convinced me that the 
anomalous Saurians, that is, those with elongated forms and rudimentary 
extremities, always pertain, by their general structure, to some one fa- 
mily of that order, among which they ought to be arranged. It cannot, 
for example, be denied, that there is a gradual passage from the Scinks 
to the Anguis and Acontias, through the medium of Scinkus hrachypus, 
S. decreenis, S. serpens, and the Seps, the Pygodactylus, and the Bipes, 
animals differing from each other less in their structure than in their 
forms, and composing a single family the Scinkoideans, from which we 
ought to exclude neither the Ablepharus nor the Gymnophthalmus. 
The same gradation exists in the family of the Lizards, through the 
genera Lacerta and Tachydromus to the Monodactylus, and, we may add, 
as an anomalous species, the Pygopus. We may connect in the classi- 
fication the Tetradactylus, the Chalcis, the Pseudopus, and Ophisaurus. 
We come at length to thefamilyofAmphisbsenae, comprehending Chirotes, 
Leptosternon, Amphisbsena ; and that of Typhlops, including Typhlops, 
Rhinopis, and Uropeltis. 
