544 



MANUAL OF ZOOLOGY. 



formidable of all living Ophidians. They possess rudimentary 

 hind-limbs terminating in horny anal spurs, which co-operate 

 with the prehensile tail in enabling the animal to suspend itself 

 from trees. In all, also, the dental apparatus is extremely 

 powerful, giving a firm hold for the constriction of the prey. 



(6.) The Typhlopida constitute an aberrant group of snakes, 

 distinguished from the typical Ophidians by the comparative 

 narrowness of their gape. They are found in both the Old and 

 New Worlds, in warm latitudes, are possessed of quite rudi- 

 mentary eyes, and burrow in the ground. Some of them are 

 of very small size, and somewhat resemble earthworms. Nearly 

 allied to the genus Typhlops itself is the Indian Uropeltis, which 

 is also subterranean in its habits. 



A good general character by means of which the poisonous Viper ine 

 Snakes may be distinguished from the harmless Colubrine forms is in the 

 shape and armature of the head. In the Viperina, as before said, the 

 head (figs. 296, 300) is triangular, broadest behind, and separated from 



Fig. 300. A, Head of Colubrine Snake (Coluber natrix); B, Head of Viperine Snake 

 (Pelias bents); C, Head of Blind-worm (Angitis fragilis), one of the serpentiform 

 Lizards. (After Bell). 



the neck by a more or less marked diminution in the diameter of this 

 latter part. The scales, too, which cover the head, are of small size. In 

 the Colubrine Snakes, on the other hand, the head is not markedly triangu- 

 lar, and gradually tapers off into the neck, whilst the upper surface of the 

 head is usually covered with large shield-like plates or " scuta " (fig. 

 300, A). ', 



DISTRIBUTION OF OPHIDIA IN TIME. The Ophidia are not 

 known to occur in any Palaeozoic or Mesozoic deposit. The 

 earliest-known traces of any serpent are in the Lower Kaino- 

 zoic rocks, the oldest being the Palaophis toliapicus of the 



