452 REPORT OF NATIONAL MUSEUM, 1898. 



sending a half iuto each branch, lu Gymnodactylus pulchellus the welts 

 are not so heavy; below the bifurcation is a welt which incloses a cir- 

 cular area, which is incomplete proximad. 



Boulenger gives the following interesting general account of this 

 family : 



The skull i^ generally much depressed, and its bones are thin. The nasals remain 

 distinct; the frontal is either single or with distinct suture; the jugal is rudimen- 

 tary, the orbit not being bound posteriorly by a bony arch ; the supratemporal arch 

 is likewise absent; the i)terygoids are widely separated and devoid of teeth, aud 

 columella crauii is present. The mandible contains only live bones, the angular 

 and articular being coalesced; the dentition belongs to the pleurodont type; the 

 teeth are small, numerous, closely set, with long, slendir, cylindrical shaft and 

 obtuse i^oint; the new teeth hollow out the base of the old ones. Only in a few 

 instances does the derm of the head coalesce with the skull, and a supraorbital bone 

 is present only in a few species of Tarentola. Both pairs of limbs are constautly 

 well developed and pentadactyle. The clavicle is dilated and perforated proxi- 

 mally, and the interclavicle is subrhomboidal, or of a shape intermediate between 

 that and the cruciform. The vertebne are biconcave; the ribs are long, aud so pro- 

 longed as to form more or less ossified hoops across the whole of the abdominal 

 region. 



The digits vary considerably, and afford excellent characters for systematic 

 arrangement. Some Geckos (living in barren regions) have the digits similar to 

 those of many Agamoids, i. e., they are subcylindi-ical or feebly depressed, aud fre- 

 quently keeled iuferiorly or denticulated laterally ; other forms with uondilateil digits 

 have them angularly bent at the articulations and provided with strong claws; but 

 the greater number have the whole or part of the digits dilated into adhesive organs 

 with symmetrical plates or lamelhe iuferiorly, the arrangement of which varies con- 

 siderably. Then, also, the claw may be retractile, either between some of the 

 lamelhe or into a special sheath. Membranes may unite the digits, but the web 

 serves only for the purpose of obtaining a greater adhesive surface, and never for 

 swimming, none of the Geckos entering the water. 



The body is generally more or less depressed, aud may be bordered by cutaneous 

 expansions, the object of which appears to be, in most cases, the same as that of the 

 iuterdigital membrane; but in the curious genus I'tycliozoon, in which the lateral 

 membranes attain the greatest development, they act as a ])arachute. The tail pre- 

 sents almost every possible shape from the leaf-like tail of Gymnodactyhis platnrus 

 aud the grotesque rudimentary tail of Xephrarns to the slender, rat-like tail of 

 Agamura and the compressed crested tail of Pristurus. This organ is, except in 

 Agamura, extremely fragile and rapidly reproduced, in which case, however, it gen- 

 erally assumes an abnormal shape and lepidosis. In some forms the tail proves to 

 be prehensile, a faculty which is i)0ssessed by few lizards other than the Chameleons; 

 and I am induced to believe that a careful examination of the Geckos, when alive, 

 will show this character to be not unfrequent. 



The eye is generally large and with vertical pupil, which, when contracted 

 strongly, is frequently denticulated or assumes the shape of two superposed rhombs; 

 some diurnal forms have the eye smaller aud the pupil circular. The eye is exposed 

 as ill snakes, covered by a transparent lid under which it moves freely, the valvular 

 lids being rudimentary; in ^FAnrosaurns, however, there are connivent movable 

 lids, and in Ptenopus the upper lid is sufficiently developed to cover the eye nearly 

 completely. 



Ihe tympanum is more or less exposed, except in Teratolepia, in which genus it 

 appears to be completely concealed under tlie scales. The tongue is fleshy, moder- 

 ately elongate, very feebly incised anteriorly, and capable of protrusion out of the 

 mouth. 



