3 I2 



SYSTEMATIC ZOOLOGY 



and some of the lizards in one continuous sheet, in the rest 

 in fragments. Appendages, when present, always have the 

 form of legs adapted to walking on land in the living repre- 

 sentatives of the group. The cloacal opening is a transverse 

 slit, and there are two copulatory organs, or penes. The lizards 

 and snakes are placed in two suborders. 



Suborder i. Lacertilia 



The Lacertilia (Lat. laccrta, lizard) or lizards, usually have two 

 pairs of appendages (Fig. 320), but sometimes the anterior pair 

 is absent, sometimes the posterior, and sometimes both ( Fig. 321 ). 

 But even when the legs are absent, the pectoral and pelvic girdles 



FIG. 320. Lacerta viridis, the green lizard of Europe. (After Brehm, from Parker and 



Haswell's Text-book.) 



are present ; and, further, some of the ribs, which are numerous, 

 meet on the midventral line and fuse to form a breastbone, or 

 sternum. There are usually movable eyelids and a tympanic 

 membrane to the ear, and these structures, together with the 

 skeletal characteristics just referred to, will serve to distinguish 

 the lizards from the serpents. The jaws are capable of but 

 little distention, and the ventral side of the body as well as the 



