REPTILES 193 



of them special names, as their arrangement is constant for a 

 given species, and is therefore an important aid to classification. 

 The scales on the upper side of the trunk are small, but those on 

 its under side are much larger, and arranged in longitudinal rows, 

 while those of the tail are also of a good size, and arranged in 

 regular encircling rings. 



The colour of the Lizard harmonizes with its surroundings, and 

 this "general resemblance" is both "protective" and "aggressive", 

 as it renders the animal inconspicuous as well to its own foes as 

 to the insects upon which it preys. The ground colour of the male 

 is greenish on the upper side, shading into lighter colour below; 

 but in the female duller tints of grey or brown predominate. 

 Both sexes are darkly marked on the upper side, there being 

 an especially well-marked stripe running down the middle of the 

 trunk. 



Endoskeleton (fig. 130). The same regions are present as in a 

 bird, but though there are many points of agreement there are 

 numerous differences, partly due to the great peculiarity of the 

 bird. The lizard's bones do not contain the air-cavities which are 

 so often found in birds. 



In the skull the brain-case is much smaller in proportion than 

 in a bird, a fact directly related to the relative size of the brain in 

 the two animals. With few exceptions the bones of the skull are 

 the same as in the bird, but the boundaries between them remain 

 fairly distinct in the adult, instead of fusing together so as to 

 obliterate all boundaries. There is one occipital condyle (see 

 p. 28), or rounded prominence for union with the backbone, each 

 half of the lower jaw is made up of several pieces, and the pres- 

 ence of a movable quadrate bone enables the mouth to be opened 

 very widely (see p. 143): all points of agreement with Birds and 

 difference from Mammals. An interesting peculiarity is found in 

 the presence of a small hole, the parietal foramen, in the top of 

 the brain-case. Imbedded in the floor of the mouth, and giving 

 attachment to the muscles of the extremely mobile tongue, is the 

 gristly "hyoid apparatus", made up of a central pointed portion, 

 from which three slender rods run out on each side. 



The backbone consists of a large number of vertebrae, and is 

 fairly flexible throughout, exhibiting neither of the extremes which 

 characterize the Pigeon (see p. 144). The usual regions can be 

 made out, except that it is not possible to say where the thoracic 



VOL. I. 13 



