SCALED REPTILES SNAKES. 421 



Two small and comparatively unimportant families of the sub-order claim a 

 few lines. The first of these, which includes but three genera, with a total 

 of five species, is that of the llysiidce, all the members of 

 which resemble the pythons and boas in the retention of Cylinder-Snakes 

 external vestiges of the hind pair of limbs, but differ in the and Shield-Tails, 

 conformation of the skull. The typical form is the coral Families 

 cylinder-snake (Ilysia scytale), a small species from the upper Ilysiidce and 

 part of the valley of the Amazon and the Guianas, the others Uropdtidw. 

 being the various species of Oylindrophis from South-Eastern 

 Asia, and the one representative of the nearly-allied Aiiomalochilus, which is 

 Sumatran. The Uropeltidce, which, in common with all the remaining snakes, 

 have lost all external traces of limbs, form an allied ,-family agreeing with both 

 the preceding in the structure of the lower jaw, and taking their name from 

 the peculiar conformation of the tail. Although in one genus it has a 

 coating of keeled scales, in all the rest this appendage terminates in a bare 

 roughened disc, and is thus quite unlike that of all other snakes. In all 

 cases the tail is very short, the body is cylindrical, and there is no distinct 

 neck, while botli the mouth and the eyes are relatively small. These snakes, 

 which are all of small size, and frequently brightly and handsomely coloured, 

 are found only in the mountains of India proper and Ceylon, where they 

 generally spend their time in tunnels channelled at a considerable depth 

 below the surface, although in rainy weather they frequently skulk beneath 

 stones and wood, and sometimes even venture out among grass and other 

 herbage. In addition to the typical Uropeltis, they include six generic types, 

 the total number of species recognised in 1893 being forty-one, of which only 

 one pertains to the type genus. It may be added that a snake from South- 

 Eastern Asia known as Xenopeltis uiticolor is regarded as representing by 

 itself the family of the Xenopdtidw, the reason for this reference being that 

 in the structure of the skull it exhibits distinct indications of relationship 

 with the Boidce, although agreeing with the next family in the number of 

 bones entering into the composition of the lower jaw. 



Together with the aforesaid Xenopeltis, the snakes included in the two great 

 and important families of the Colubridcv and Viperidca are broadly differentiated 

 from the BoidcE and their allies by having one bone less in 

 each lateral branch of the lower jaw, the missing bone being Colubrine Tribe, 

 termed the coronoid. It is unfortunate that this important Family 

 distinctive feature is not visible in the living animal ; but so Colubridw. 

 it is, and the student must make the best of it. As already 

 said, none of these snakes retain external vestiges of limbs. The colubrine 

 tribe is an extremely large group, embracing as it does many more snakes 

 than any of the other families into which the sub-order is divided. All are 

 characterised by the circumstance that the maxilke of the upper jaw are 

 horizontal, and incapable of movement. Whereas, however, some, such as 

 the common water-snakes, are perfectly harmless except to the small crea- 

 tures upon which they prey others, like the sea-snakes and cobras, are 

 among the most deadly of all serpents. In such a vast assemblage it is im- 

 possible to do more than notice some of the leading types. 



As an example of the first of the three great sections into which it has been 

 found advisable to divide the family, we may take the water-snakes of the genus 

 Tropidonotus, of which the common British ringed-snake ( T. natrix) is the most 

 familiar representative. From the fact that all the teeth are completely solid 

 throughout, showing no traces of either an external groove or a deeper 



