xii GECKONES 503 



separate; eyes (with few exceptions) without movable lids; 

 pleurodont ; tongue fleshy and broad, slightly nicked anteriorly, 

 and capable of protrusion. 



This definition does not apply to a few forms. In the 

 Eublepharinae the vertebrae have advanced to the precocious 

 condition, and the parietals are fused together, while the eyes are 

 provided with typical, movable lids. In 'the Uroplatinae the 

 clavicles are not dilated, and the nasals are fused into one bone. 

 The Geckos seem to be not only a very independent but also a 

 very old branch of Saurians. Although fossil representatives are 

 unknown, the resemblance of their vertebrae to those of the 

 Palaeozoic Microsauri is at least remarkable. They are now 

 practically cosmopolitan within the warmer zones, being found in 



i CECKONIDAE. 



Fia. 118. Map showing the distribution of Geckonidae. 



abundance in all intertropical countries and islands, even in New 

 Zealand. About two hundred and seventy species are known, 

 which have been subdivided into about fifty genera. The generic 

 differences are trivial with few exceptions, and refer mostly to 

 the structure of the digits. 



The more important features of the vertebral column are the 

 absence of axial joints and the persistence and life-long growth 

 of the chorda dorsalis. Each vertebral centrum consists of a 

 cartilaginous tube, more or less calcified or ossified, with a narrow 

 waist and a cartilaginous septum in the middle. In the tail this 

 septum, which is only slightly invaded by ossification, coincides 

 exactly with the line of transverse division of the vertebrae into 

 an anterior and a posterior half. This is the level where the 

 tail breaks off and whence it is renewed. Between every two 

 successive centra lies an intercentrum, broadest ventrally, crescent- 



