THE RHTNCHOCEPHALA. 225 



B. No columella ; no interorliital septum. 



12. Amphisbcoioida. 



11. — The pterygoid and quadrate bones disunited. 



13. Chamceleoiiida. 



1. The Ascalahota. — The Geckos, which constitute this 

 group, are Lizards of small size, which inhabit the hotter 

 parts of both the Old and the New Worlds, and have always 

 attracted attention by their habit of running with exceeding 

 swiftness along the walls and ceilings of rooms. They are 

 enabled to maintain their hold under these circumstances, in 

 part by the sharpness of their cui-ved, and, in some cases, 

 retractile claws ; and, in part, by laminated expansions of 

 the integiiment of the under- surfaces of their digits, which 

 appear to act in somewhat the same fashion as the sucker 

 of the Bemora, or Sucking-fish. 



The most important and distinctive characters of these 

 Lizards are : — 



Their vertebrae are amphicoelous. 



Neither the upper nor the lower temporal arcades are 

 ossified, the postfrontal being connected with the squa- 

 mosal, and the maxilla with the quadrate, by ligament. 



The jugal is rudimentary, and the squamosal very small. 



There are no eyelids, but the integument becomes trans- 

 parent as it is continued over the eyes. The integument is 

 soft, or coriaceous, not scaly. 



2. The Bhynchocephala.— This division contains only the 

 very remarkable genus Sphenoclon (otherwise Hatteria, or 

 Bhynchocephalus). The vertebrae are biconcave. Some of 

 the ribs have recun-ent " uncinate " processes, as in Birds 

 and Crocodiles. The sternal and vertebral ribs are con- 

 nected by an articulation, and there is a very peculiar 

 system of abdominal ribs. The infra-temporal arcade is 

 completely osseous in this, but in no other recent, lizard. 

 The quadrate bone is immoveably fixed, not merely by an- 

 kylosis with the squamosal, quadrato-jugal, and pterygoid, 

 but by the ossification of the strong membrane, which, in 

 Lizards in general, extends between the quadrate, the ptery- 



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