198 SNAKES. 



THE COLUBRINE SNAKES. 

 Family COLUBRID^. 



The skulls of the remaining snakes are markedly distinguished from those 

 of the foregoing by the total absence in the lower jaw of the bone known as the 

 coronoid ; while in all cases a supratemporal is present on the upper surface of the 

 skull. The present family, which includes by far the great majority of the species 

 of the suborder, and comprises both harmless and noxious kinds, is specially 

 distinguished from those to be mentioned later on by the circumstance that in 

 the skull the upper jawbone, or maxilla, is fixed in a horizontal position, and 

 also that the pterygoids reach either to the quadrate-bone or the lower jaw. 



Before coming to the Colubrine family it should, however, be mentioned 

 that there is one remarkable snake (Xenopeltis unicolor), from South-Eastern 

 Asia, retaining in the structure of its skull traces of affinities with the boas and 

 pythons. This affinity is displayed by the fact that the prefrontal bone, which 

 lies immediately behind the nasal aperture of each side, is of large size, and 

 extends forwards and inwards to articulate with the nasal bone in the same 

 manner as the boas. Accordingly, this snake is regarded as the representative of 

 a distinct family (Xenopeltidce), which is considered to have originated from the 

 Boidce quite independently of the Colubrines. 



From Xenopeltis the Colubrines are distinguished by the small size of the 

 prefrontal bone of each side, which articulates merely to the outer front angle of 

 the frontal bone without any contact with the nasal bone. In such a large group 

 it is highly important to have some means of division into subgroups of higher 

 value than genera ; and, according to the modern classification, three such serial 

 divisions may be indicated by the characters of the teeth. The first and most 

 primitive of these series, which may be termed the solid-toothed colubrines 

 (Aglypha), is characterised by the whole of the teeth being solid, without any 

 trace of grooves, all its representatives being harmless, On the other hand, in the 

 second series or hind-fanged colubrines (Opisthoglypha), one or more of the hinder 

 teeth of the upper jaw are grooved ; while in the third series or front-fanged 

 colubrines (Proteroglypha) the front teeth of the upper jaw are grooved or tubular. 

 Of the last series the whole of the members are poisonous, while many of those 

 of the second are noxious in a minor degree, All these three sections contain 

 species adapted to particular modes of life, so that we may have two or three 

 snakes which, while externally very similar, are only distantly allied to one another. 

 The Javan wart-snake (Acrochordus javanicus) may be taken 

 as a well-known representative of the first, or acrochordine subfamily 

 of the solid-toothed colubrines, which includes only five genera, distributed over 

 South-Eastern Asia and Central America. Unfortunately, the characters distin- 

 guishing this subfamily from the next are connected with the bones of the skull, 

 and cannot therefore be verified without dissection, but in the study of snakes, 

 according to the modern system, the student must accustom himself to such 

 difficulties. The essential feature of the skull in the present group is the pro- 

 duction of the postfrontal bone above the cavity of the eye ; while, as a secondary 



