n6 REPTILES 



South and West Africa, which are really nothing more than 

 worm-like limbless skinks, " degraded " for a burrowing life. 

 Another somewhat similar type is represented by Dibamus 

 novce-guinece, a worm-like burrowing reptile, with the hind-legs 

 represented by a pair of small flaps, the limbs and even their 

 supporting bony girdles being otherwise totally lacking. 



Finally, we have a few small worm-like or snake-like lizards 

 from California, constituting the genus Aniella and the family 

 Aniellidte, which seem to be degraded types more or less closely 

 allied to the AnguidtE. Although soft overlapping scales are 

 retained, the eyes and ears are concealed, and the limbs wanting. 

 In the preceding and some earlier paragraphs allusion has been 

 made to the degeneration of the eye in burrowing snakes, and 

 certain modifications of the eyelids in some desert lizards. 

 These may be briefly referred to collectively. In the burrow- 

 ing snakes of the genus Typldops the eyes are hidden by 

 shields of the skin ; but in the Uropeltidce although small, 

 they are distinct. In the burrowing lizards of the family 

 Aniellidce, the eyes, although concealed, are still present ; and 

 in the slow-worm, despite its misnomer of blind-worm, they are 

 bright and bead-like. Accordingly, although the eye has been 

 independently degenerated in several distinct groups of reptiles, 

 in none has it become completely aborted, and in all cases prob- 

 ably retains some degree of functional power. 



Very interesting is the independent development of a trans- 

 parent " window " in the lower eyelid of two distinct groups of 

 desert-haunting lizards, to which allusion has already been 

 made. In the skinks of the genus Mabuia the lower eyelid 

 has become much enlarged, so that it will cover the whole eye, 

 its transparent window thus permitting of vision while the eye 

 itself is protected from the sand-blast. In another group of 

 skinks, forming the widely distributed Old World genus 

 Ablepharus, the lower eyelid, which is completely fused to the 

 margin of the aborted upper one, is wholly transparent ; and 

 these lizards consequently cannot "open their eyes" at all. 

 Analogous modifications occur in desert lizards of the family 

 Lacertidce. This occurs, for example, in certain species of the 

 Asiatic and African genus Eremias ; in the Indian Cabrita the 

 " window " is unusually large ; and Ophiops, which is found in 

 desert tracts in North A'rica Syria and India, presents an exact 



