314 



ZOOLOGY 



SECT. 



present, the epidermis is always hardened and cornified so as to 

 form plates of horny material, such as the horny plates of the 

 Tortoises, which protect the underlying parts from injury and 

 desiccation. Bony plates are frequently present as well. Inmost 

 respects the internal structure of the Reptilia shows a very decided 

 advance on that of the Amphibia. The skull, as well as the 

 pectoral and pelvic arches, are more completely ossified, and both 

 vascular and nervous systems show a higher grade of organisation. 



1. Example of the Class. — A Lizard {Lacerta). 



The most striking external differences between the Lizard (Fig. 

 960) and the Frog are the covering of scales, the comparative 

 smallness of the head, and the presence of a distinct neck, the great 



Fig. 9(30.— Iiacerta Tiridis. (After Brehm.) 



length of the caudal region, the shortness of the limbs, and the 

 approximate equality in length of the anterior and posterior pairs. 

 The anterior limbs are situated just behind the neck, springing 

 from the trunk towards the ventral surface. The fore-limb, like 

 that of the Frog, is divided into three parts, the upper-arm or 

 hrachium, the fore-arm or anti-hrachium, and the hand or inanus ; 

 there" are five digits provided with horny claws, the first digit or 

 pollex being the smallest. The hind-limbs arise from the posterior 



