40 BULLETIN 199, UNITED STATES NATIONAL MUSEUM 



Two or three scales in contact with frontal anteriorly; three or four supra- 

 oculars Scincidae (p. 155) 



8. A granular fold along sides of body, abruptly differentiated from much 



enlarged dorsal and ventral scales Anguidae (p. 194) 



Not so 9 



9. Ventral scales large, quadrangular, in 8 longitudinal series; dorsals granular. 



Teiidae (p. 170) 

 Ventral scales smaller, in more numerous rows 10 



10. Ventral scales quadrangular; scales on top of head small, more or less uniform, 



tubercular; dorsal scales granular with numerous enlarged tubercles. _ 11 



Ventral scales pointed or rounded, not quadrangular; body and head scales 



as described or not 12 



11. Digits on hind leg of nearly equal length; enlarged tubercles covering most of 



dorsal surface of body; a series of about four large, paired postmentals on 



midline of chin, immediately back of mental Helodermidae (p. 192) 



Digits on hind leg varying greatly in length, fourth toe three times as long 

 as fifth; enlarged tubercles on body much less numerous, not occupying as 

 great an area as granules; no enlarged postmentals. _Xenosauridae (p. 207) 



12. Head and most of body, except bellj^, covered with very minute granules; no 



parietal "eye"; no keels or tubercles along ventral surfaces of digits. 



Qekkonidae (p. 40) 



Head covered with larger scales; a parietal "eye" usually visible; at least 



one tubercle, or several keels, on most or all of lamellae on ventral surfaces 



of digits Iguanidae (p. 53) 



Family GEKKONIDAE Stejneger 



Geckonidae Boulenger, Catalogue of the lizards in the British Museum, vol. 



1, 1885, p. 3. 

 Gekkonidae Stejneger, U. S. Nat. Mus. Bull. 58, 1907, p. 164. 



Subfamilies. — Studies by Noble (Amer. Mus. Nov., No. 4, 1921, 

 pp. 1-16) and by M. A. Smith (Rec. Indian Mus., 1933, p. 16) indi- 

 cate that neither the Eublepharidae nor the Uroplatidae are worthy 

 of either family or subfamily distinction. 



Genera. — About 75 genera are commonly recognized. 



Range. — World-wide, in tropical and semitropical areas. 



Remarks. — Eight genera of this family occur in Mexican territory. 

 Three of these have probably been introduced accidentally from other 

 parts of the world. Peropus, with a single representative, arrived on 

 the west coast of Mexico probably from the Philippines. Hemidac- 

 tylus, with three species, has a somewhat more complicated history. 

 One species reached the west coast, probably from the Philippines 

 (frenatus), a,nother came across the Atlantic to the east coast from 

 Europe or Africa (turcicus), and a third (mabouia) probably came 

 from somewhere in the West Indies or, not impossibly, from Mada- 

 gascar or South Africa where it also occurs. Aristelliger undoubtedly 

 was imported from the West Indies. A fourth genus, Gonatodes, has 



