CROCODILIANS, LIZARDS, AND SNAKES. 709 



investigated especially tbe dental structures and divided the order 

 into Opoterodonta, Agiyphodonta, Opisthoglypba, Proteroglyplia, and 

 Soleuoglypba. The first is Augiostomatous and the last four are 

 Eurystomatous. In the system of Stannius ' we have other than 

 dental characters considered. Thus the Angiostoraata are divided 

 into Typhlopina and Tortricina, and the Burystomata into Peropoda, 

 Asinea, and Thauatophidia, the last including all of the venomous 

 snakes. In 1845 G-ray, in his catalogue of snakes in the British 

 Museum, had combined forms with grooved i^osterior teeth and the 

 colubriform venomous snakes with the harmless snakes under the 

 name Colubroidea, and this arrangement was continued by Giinther 

 in his catalogue of tbe Colubrine snakes of tbe British Museum in 

 1802. The author of the present work adopted a system which 

 included the merits of those already in existence, adopting the 

 divisions of Miiller and Stannius with those of Dumeril, placing the 

 Opisthoglypba with tbe true Colubroidea like Gray, but adopting 

 for the entire group Staunius's name, Asinea. I also rearranged some 

 of the venomous genera in accordance with their cranial structure, 

 which bad been overlooked by previous authors. Finally, in the sys- 

 tem of Boulenger, as adopted in the Catalogue of Snakes in the British 

 Museum, the Opisthoglypba and Proteroglypha of Dumeril are included 

 in the Colubriform superfamily, as was done by Gray and Giinther. 

 This division, Colubroidea, was then divided into Aglypha, Glypho- 

 donta, and Proteroglypha. 



The classification of the great mass of the Colubroid snakes has 

 always been a difficult i)roblem. Dumeril relied on the relative pro- 

 portions of the teeth, and established numerous "families" based upon 

 them. These divisions are often not natural, while others are entirely 

 tenable. On the whole, however, the larger divisions, based on pro- 

 portionate lengths and apart from the grooving for conveying saliva, 

 lack definition, owing to the insensible gradations which they present. 

 The characters adduced by Dumeril are, however, of general applica- 

 cation in the definition of genera. Their application has been extended 

 by Boulenger, but to a degree of refinement which is in some cases not 

 practicable, owing to gradations. Hence it became important to dis- 

 cover other characters. This I have done in those exhibited by the 

 tbe male intromittent organ and by the pulmonary structure. The 

 former furnish many characters which express affinity or the reverse, 

 a! id re-enforce or modify those which we have hitherto possessed. 



V. HABITS. 



The peculiar form of tbe snakes among vertebrate animals, their 

 comparative abundance, and the fact that some of them are especially 

 dangerous to life, invests them with more popular interest than any 

 other gronp of reptiles. 



The characteristics of the venomous forms will be pointed out in the 



' Zootuiiiif del- Aiiipliibiou. 1856. 



