442 



AMPHIBIA ORDER I.ECAUDATA. 



a very large number of species distributed over the greater part of the world 

 with the exception of Oceania, Australasia, and Madagascar. In this genus 

 tile-pupil of the eye forms a horizontal slit, the tip of the tongue is not 

 notched, the toes of the fore-feet are free, but the hinder ones are partially 

 webbed. Occasionally the ends of the toes are expanded into small discs 

 the head may bear bony ridges, and in many cases the skin is covered with 

 warts, which under excitement secrete a miiky acrid fluid. Two species are 



met with in Britain, namely the 

 common toad (B. mdgaris), and the 

 natterjack (B. calamila) ; the latter 

 being very local in our islands, 

 and easily recognised by the 

 whitish or yellow streak on the 

 middle of the back. Although 

 not found in Britain, a third 

 European species is the handsome 

 green toad (B. viridis), which also 

 ranges into the north of Africa 

 and Asia. The males differ from 

 those of the common species in 



Fig. 6. NATTERJACK TOAD (Bufo catomita) 



possessing a vocal sac beneath the 

 throat. 

 Although many of the tree-frogs belonging to this family are very similar 



externally to the Dendrobatidce, they agree with the toads in the conforma- 

 tion of the skeleton of the chest. From the Bufonidce they 



Family ffylidce. may be readily distinguished by the possession of upper 

 teeth ; while a still more distinctive peculiarity is to be 



found in the claw-shaped terminal joints of the toes. The frogs of this 



family, which are mostly arboreal in their habits, and are ranged under a 



considerable number of generic divisions, attain their maximum development 



in America (especially its tropical regions) and Australasia, but also occur in 



Europe and Northern Asia, while a single representative of the typical genus 



Hyla is found in India. The genus 



just named includes more than a 



hundred and fifty species, and has 



a distribution coextensive with 



that of the family. Whereas the 



European If. arborea is a tiny little 



creature, some of the Brazilian 



species measure as much as three 



inches in length. These frogs have 



the tips of the toes expanded into 



discs, and the hind-feet more or 



less fully webbed. In the eye the 



pupil is horizontal ; and the hinder 



end of the tongue may be either 



adherent or partially free. The 



males of the European species, and 



likewise those of some other kinds, 



have a huge vocal sac on the throat. 



In order to assimilate them to their surroundings, tree-frogs are of a brilliant 



green colour. Except during the breeding season when they descend tem- 



Fig. 7. EUROPEAN TBEE-FROG (Hyla arborea). 



