224 SPHAERODACTYLUS. 



time-honored usage have no diagnogtic value whatsoever. The median groove 

 in the rostral, the superciliar j' spine for instance are really generic and not specific 

 characters yet their mention in specific descriptions has always been customary. 

 The conditions in the supralabial series are so variable that no reliance can be 

 placed on characters apparent there. So also, though in a less degree, the 

 nimiber and shape of the scales separating each supranasal from its fellow of the 

 opposite side, is subject to much variation. The shape of head and body is 

 useful to observe, although the tail varies widelj' in proportion to the bodj'-length. 

 Still it is generally longer and much more slender m females than in males. The 

 best characters are to be found in the size, form, and arrangement of the scales of 

 both the dorsal and ventral surfaces. Colour also as becomes daily more evident, 

 is of far more value in diagnosis than has previously been supposed. Many 

 features of pattern are strongly fixed. Lines may break up into series of spots ; 

 these may be manj^ or few or the whole series may be absent but even a remnant 

 is Ukely to be verj- definitely located with reference to the original complete 

 pattern. Thus also markings, such as the spectacles so often seen on scapular 

 or sacral regions, may or may not be present but if present their location is not 

 haphazard, but is very distinctly fixed. The brilliantly cross-banded species 

 occur in the Greater Antilles and Bahamas and curiously enough are found 

 among the two extremes of the genus. They are either species with tiny granular 

 scales or with enormous tectiform dorsals and among these two divergent groups 

 sex-linked dichromatism has become well established. There are probably 

 many more sex-Unked colour-characters than are now recognized. Their dis- 

 covery will further reduce the range of apparently fortuitous variability of each 

 species. 



It is a somewhat surprising fact to observe how close is the correspondence 

 between the distance from the tip of snout to the ear and the length of the fore 

 Umb. If the first distance is longer than usual so also the fore limb is likewise 

 long. Whether this fact has any special significance does not appear. There 

 may be some relation between the length of the arm and a corresponding head- 

 length which makes more convenient the picking of small objects from the ground 

 with the mouth or by using the thick fleshy and only slightly extensible tongue. 

 While one occasionally sees a sphaerodactyl struggling to subdue a little moth, 

 its wings flapping a most inconvenient if ineffectual protest, it is far more com- 

 mon to find them eating ants. Little ants swarm in houses in the tropics as 

 everyone who has lived there knows to his sorrow, and this maj' in some degree 

 account for the lizards frequenting houses too. Ants creeping over smooth 



