22 ON THE PHYSIOGNOAIY OF SERPENTS. 



performed in the Saurians by the general form and organs 

 of locomotion, are wholly subordinate to their general 

 organization.* It is tlius e\'idcnt that the characters 

 formed on these parts, must ahvays lead to an artificial 

 system ; and it is equally clear, from what we shall state, 

 that the two t}q3es on which Saurians and Ophidians are 

 modelled, are connected by numerous intermediate forms. 

 Hence many naturalists have refused to adopt the two 

 foregoing divisions, wliich 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 difficidt to assign the dis- 

 tinctive marks which separate, in a precise manner, the 

 Oj^hidians 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 oi'der, 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, tlirough the medium of Scinkus brachypus, 

 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. 

 "NVe come at length to the family of Amphisbaenae, comprehending Chirotes, 

 Leptosternon, Amphisbsena ; and that of Typhlops, including Typhlops, 

 Rhinopis, and Uropeltis. 



