288 ZOOLOGY SECT. 



and the branchial arches are much reduced. The limbs, also, 

 in the terrestrial Salamanders stand out from the trunk, and have 

 the soles of the feet and hands applied to the ground with the toes 

 directed forwards, so as to support the weight of the body. More- 

 over, all trace of the median fin disappears, the tail becoming 

 nearly cylindrical. 



In the Anura the body is always Frog-like, the head being large 

 and depressed, with a very wide mouth and large tympanic mem- 

 branes, the trunk short, the tail absent, and the hind- much larger 

 than the fore-limbs. In the Toads, such as the common British 

 Bufo vulgaris, and most Tree-frogs, the webs between the hind-toes 

 are reduced or absent, and in many species of Hyla the toes end 

 in rounded sucking-discs. 



In the Gymnophiona (Fig. 956) the body is greatly elongated and 

 snake-like, the head is small and not depressed, and the limbs are 



6 



?SL 



B 



"" '-" ^ 



''' i ' ' '''' '' " ' ' ' 



an 



FIG. 936. Ccccilia pachynema. A, anterior extremity from the right side ; B, posterior 

 extremity from beneath, an. anus. (After Boulenger.) 



absent. There is no tail, the anus (an.) being at the posterior end of 

 the body on the ventral surface. The Stegocephala, or Labyrintho- 

 donts as they are frequently called, were mostly salamander-like, 

 having long tails and well-developed limbs : some, however, were 

 snake-like and limbless, and probably retained their external gills 

 throughout life. They varied in length from 10 centimetres to 

 peveral metres. 



The skin of Amphibia is soft and usually slimy owing to the 

 secretion of the cutaneous glands, which is sometimes poisonous. 

 In some forms, such as Bufo and Salamandra, there are large swell- 

 ings on the sides of the head, formed of aggregated glands and 

 called parotoids. In the larvae of both Urodela and Anura, and in 

 the adult aquatic Urodeles, lateral sense-organs are present, and 

 impressions on the cranial bones show these organs to have been 

 well developed in the Stegocephala. The colour of the skin is often 

 very brilliant : the Spotted Salamander is yellow and black, and 

 many Frogs are green and gold, scarlet and black, and so on. The 

 green colour of Tree-frogs is protective, serving to conceal them 



