12 NATURAL HISTORY OF VERTEBRATE ANIMALS 



Class, Amphibia 



Sub-class, Labyrinthodonta or Stegocephali 



Fossil forms, long extinct; bodies of very large size in some 

 instances and commonly covered with scales (Fig. 5). 



Sub-class, Lissamphibia 



Existing forms; no well-developed scales; mostly a soft 

 moist skin, as in frog; none of very large size. 



Order, Gymnopkiona or Apoda 



Worm-like creatures without limbs; burrowing in moist 

 ground; not found in temperate America (Fig. 6). 



Order, Urodela 



Tailed amphibians; the salamanders, etc. (Fig. 1 B). 



Order, Anura 



Tailless amphibians; the frogs and toads (Fig. 7). 



Following the orders, as one proceeds in classification, come 

 families, then genera, and finally species. Thus, the Order Anura 

 contains, along with some half dozen others, the Family Ranidce, 

 which in turn includes the Genus Rana and others. For example: 



Order, Anura 

 Family, Ranidce 

 Genus, Rana 



Species, pipiens, the " leopard " frog (Rana pipiens) 



In speaking of a species, it is customary to use both the generic 

 and the specific names, much as we use a given name and a sur- 

 name in referring to human individuals, for the purpose of more 

 accurate designation. To be more definite, we say " Smith, 

 John," instead of saying merely " John " or " Smith." In like 

 manner, we refer to the leopard frog as Rana pipiens or R. pipiens, 

 writing the generic name with a capital and the specific name with 

 a small letter. The following are common species of the genus 

 Rana: R. catesbiana, the ''bullfrog"; R. clamitans, the "green 

 frog"; R. sijlvatica, the *' wood frog" ; R. palustris, the " pickerel 

 frog "; and R. pipiens. 



