xni CLASSIFICATION TYPHLOPIDAE 593 



B. Coronoid absent ;. sqtiamosal present. 



1. Maxillary horizontal ; pterygoid reaching quadrate or mandible. 

 Prefrontal bone in contact with nasal. Xenopeltidae, p. 605. 

 Prefrontal not in contact with nasal. Colubridae, p. 606. 



2. Maxillary horizontal ; pterygoid not reaching quadrate or man- 

 dible. Amblycephalidae, p. 637. 



3. Maxillary vertically erectile, perpendicularly to ectopterygoid ; 

 pterygoid reaching quadrate or mandible. Viperidae, p. 637. 



For ordinary practical purposes this synopsis is useless, being 

 based entirely upon anatomical characters, not all easily ascer- 

 tained. The following characterisation of families may therefore 

 be preferred : 



Eyes vestigial ; no teeth in the lower jaw ; without enlarged ventral scales. 



Typhlopidae. 

 Eyes vestigial ; teeth restricted to the lower jaw ; without enlarged ventral 



scales. Glauconiidae. 

 Eyes very small ; head not distinct ; ventral scales scarcely enlarged ; tail 



extremely short, ending obtusely and covered with peculiar scales. 



Uropeltidae. 

 With vestiges of the hind-limbs appearing as claw-like spurs on each side of 



the vent ; ventral scales transversely enlarged ; eyes functional, free. 

 Ventral scales scarcely enlarged. Ilysiidae. 

 Ventral scales transversely enlarged. Boidae. 

 With a pair of poison-fangs in the front part of the mouth, carried by the 



otherwise toothless, much shortened, and vertically erectile maxillaries ; 



ventral scales transversely enlarged ; eyes free. Viperidae. 

 All the remaining Snakes combine the following characters : the maxillaries 



are typical, not separately movable, horizontal, with a series of 



teeth. 1 The mandible is toothed but has no coronoid bone. 



There are no vestiges of limbs or of their girdles. The eyes are free. 

 Dentary movably attached to the tip of the articular bone of 



the mandible ; skin beautifully iridescent. Xenopeltidae. 

 Without a mental groove ; the ends of the pterygoids are free, not reaching 



the quadrates. Amblycephalidae. 

 With a median longitudinal groove between the shields of the chin ; the 



squamosal is horizontally elongated, movable ; the pterygoid reaches 



the quadrate. Colubridae. 



Fam. 1. Typhlopidae. Burrowing snakes which have the 

 whole body covered with uniform cycloid scales, and with the 

 teeth restricted to the small and transversely placed maxillary 

 bones. The pterygoids do not extend backwards to the 

 quadrates, and there are no endopterygoids. The quadrates 

 slant obliquely forwards, and are attached directly to the pro- 



1 Except Oligodon, Dasypeltis and Atractaspis (see p. 582), in which palatal 

 teeth are restricted to the palatines. 



VOL. VIII 2 Q 



