194 THE ANATOMY OF VERTEBRATED ANIMALS. 



1. The Ascaldbota. — 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 attract- 

 ed attention by their habit of running with exceeding swift- 

 ness along the walls and ceilings of rooms. They are enabled 

 to maintain their hold under these circumstances, in part by 

 the sharpness of their curved, and, in some cases, retractile 

 claws ; and, in part, by laminated expansions of the integu- 

 ment of the under-surfaces of their digits, which appear to act 

 in somewhat the same fashion as the sucker of the Hemora^ 

 or Sucking-fish. 



The most important and distinctive characters of these 

 Lizards are : 



Their vertebrse are amphicoelous. 



Neither the upper nor the lower temporal arcades are ossi- 

 fied, the post-frontal being connected with the squamosal, 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 ^hynchocephala. — This division contains only the 

 very remarkable genus Sphenodon (otherwise Satteria^ or 

 Hhynchocephalus), The vertebrae are biconcave. Some of 

 the ribs have recurrent " uncinate " processes, as in Birds and 

 Crocodiles. The sternal and vertebral ribs are connected by 

 an articulation, and there is a very peculiar system of abdomi- 

 nal ribs. The infra-temporal arcade is completely osseous in 

 this, but in no other recent, lizard. The quadrate bone is im- 

 movably fixed, not merely by anchylosis with the squamosal, 

 quadrato-jugal, and pterygoid, but by the ossification of the 

 strong membrane, which, in Lizards in general, extends be- 

 tween the quadrate, the pterygoid, and the skull, and bounds 

 the front walls of the tympanum. The dentary pieces of the 

 mandible are not suturally united. The premaxillae are not 

 anchylosed together, and, as in some other Lizards (e. g., TIrO' 

 mastix), have a beak-like form, the large premaxillary teeth 

 becoming completely fused, with the bony substance of tlie 

 premaxilljB. There is a longitudinal series of teeth upon the 

 ])alatine bone running parallel with those on the maxilla, and 

 the mandibular teeth are received into the deep longitudinal 

 groove which lies between the maxillary and the palatine 

 teeth. By mutual attrition, the three series of teeth wear one 



