HISTORY OF OPIIIOLOGY. 115 



extended, allowing themselves to be guided by the same 

 ]:>rinciples, and are hence unable to follow a natural system. 

 We shall see in the sequel to what errors this manner of 

 viewing the subject has given rise, and on what a false path 

 it has conducted. 



Klein,* most frequently guided in his labours by a spi- 

 rit of contradiction, has arranged among serpents many 

 Annelides, and even Intestinal Worms. The true serpents 

 are by him divided into two classes, characterized by the 

 form of the head and of the tail : those with the head of 

 the same diameter with the body, and with a short and 

 rounded tail, form his genera Amphisbaena and Scytale ; 

 the other class comprehends the Kynodons or venomous 

 snakes, in which he distinguishes the Viper, the Naja, and 

 the Crotalus ; the innocuous serpents are lastly distributed 

 into the genera Ichthyodon, Lytaidon, and Anodon, estab- 

 lished on the form of the teeth. 



It is obvious that this author is the first who has pro- 

 posed to separate the venomous from the innocuous serpents. 

 It was afterwards that GRAYf especially devoted himself 

 to discover the marks by which to characterize these two 

 divisions. The result of his researches is, that there is no 

 other method of recognising the venomous species, but hj 

 ascertaining the presence of the fangs. This memoir con- 

 tains many good observations on the dentary system of 

 serpents. 



The great reputation that Laurenti acquired by the 

 publication of his synopsis | is not less than his merits as 

 a systematic author. His third order of Reptiles compre- 

 hends the serpents, which he distributes into the genera 

 Chalcides, C^ecilia, Amphisba3na, Anguis, Natrix, Cerastes, 

 Coronella, Boa, Dipsas, Naja, Caudisona, Coluber, Vipera, 

 Cobra, Aspis, Constrictor, and Laticauda. The numerous 

 species with which he has enriched his scheme, being, for 

 the most part, established and characterized on the figures 

 of Seba, are chiefly nominal, as may be seen in analyzing 



* Tentamen Herpetoh^ice, Konigshergi, 1755. 



t Phil. Trans., Ixxix,, pi. p. 21. 



X Synoims Reptilium, Vienna, 1768. 



