During the two hundred years that have witnessed the development of natural history into a science, many and various have been the methods of zoological and particularly of ophiological classification. A few of these methods are sketched out in chap. ii. It will be seen that the character of the teeth had not for a long while much weight in classifying snakes. According to Schlegel, Klein in 1755 was the first to separate the venomous from the non-venomous snakes in classification. But after him Linnæus, then the greatest naturalist of modern times, distinguished snakes chiefly by the form of the ventral and sub-caudal plates; so that in the six genera which he established (_Amphisbæna_, _Cecilia_, _Crotalus_, _Boa_, _Coluber_, and _Anguis_), rattlesnakes and boas, colubers and vipers, with others of the most opposite characters, were jumbled up together; and the little burrowing blindworm and the venomous sea snakes were supposed to be related, because they neither of them had ventral scales! On account of his vast researches and great reputation, subsequent naturalists were slow to entirely overthrow his system and to venture on reforms of their own, and our cyclopedias are suffering to the present day from the confusion of the various methods of classification adopted by so many naturalists, as a few quotations presently will show. Dandin, 1802, though his work was reckoned by Schlegel the most complete up to his time, comprehended all the venomous snakes under the head of ‘vipers.’ Cuvier divided the vipers (with _crochets mobiles_) from those with fixed fangs; but yet was unsound in many other respects, confounding the _Elapidæ_ with the _Viperidæ_, although he professed to separate them. Another confusion arose out of the word _cobra_, Portuguese for snake, so that wherever the Portuguese settled most snakes were _Cobras_. In India the English have retained the name _Cobra_ for the snakes with the hood, which name is now confined to the one group, _Capella_. ‘The characters of dentition offer in a great many cases a decisive method for distinguishing the species,’ says Günther; ‘but as regards the combination of species into genera and families, it is of no greater importance than any other external character by itself.... Still I am always glad to use the dentition as one of the characters of genera and species whenever possible—namely, whenever it corresponds with the mode of life, the general habits, and the physiology.’[93] Since the publication of Dr. Günther’s work, _The Reptiles of British India_, 1864, the distinctions of the various types of dentition seem to have been more clearly comprehended; and as this work is the accepted authority among English ophiologists, and will best commend itself to the reader, it shall be our guide in the present attempt to simplify much complication.