:^14 



zooT/)r;Y 



SKCT. 



present, the epidermis is always hartlened 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 

 res23ects the internal structure of the Rcptilia 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 {Laccrta). 



The most striking external differences between the Lizard (Fi'g. 

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

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



Fio. 9(i0.— Lacerta viridis. (After Hrehm.) 



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 paits, the upper-arm or 

 hrachiitm, the fore-arm or anti-brachmm, and the hand or manus ; 

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

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



