286 FROGS AND TOADS. 



selves; the hatching of the tadpoles taking place from June till September. 

 After the cares of the nursing period are over, the male loses his voice, which is 

 not resumed till the following February, when it is continued till August. The 

 males are more numerous than the females, and during the breeding-season their 

 loud croaking is almost continuous. From September till the beginning of March 

 the habits of this sex are similar to those of other frogs. The lower Miocene 

 strata of the Continent have yielded remains of an extinct frog belonging to 

 the same genus ; while in the rocks of the upper part of the same division of the 

 Tertiary period there occurs a gigantic frog belonging to the same family, which 

 has been referred to an extinct genus, under the name of Latonia. 



The other two families — Amphignathodontidce and Hemiphrac- 

 tidce — belonging to the present suborder are not of much importance, 

 and are represented only by a small number of genera and species from Central 

 and South America. They are, however, of some interest, from the circumstance 

 that both the upper and lower jaws are furnished with teeth, in which respect they 

 agree with the sharp-nosed frog among the members of the first suborder. 



The Tongueless Frogs. 



Families XENOPODIDJE and PlPlDJE. 



The members of the order hitherto considered are furnished with a well- 

 developed tongue, but in the order Aglossa, this organ is totally wanting. 

 The vertebrae resemble those of the disc-tongued frogs in having their articular 

 cups at the hinder-ends, but ribs are wanting. The metacoracoids correspond in 

 structure to those of the suborder Arcifera, although the cartilages at their edges 

 do not overlap. The tadpoles of these remarkable frogs exhibit the peculiarity of 

 having a pair of breathing-pores, after the loss of the external gills, situated 

 symmetrically on each side of the body. Each family is represented by a single 

 genus, respectively confined to Tropical Africa and Tropical South America. 



The spur-toed frogs (Xenopus), of which there are three species 

 Spur-Toed Frog. . . . . 



' from Tropical Africa, are characterised as a family by the presence 



of teeth in the upper jaw ; while they are further distinguished by the circular 



pupil of the eye, the absence of an external tympanic membrane to the ear, the 



free front-toes, and the webbed hind-foot, in which each of the three inner-toes is 



furnished with a sharp, spur-like nail. The smooth spur-toed frog {X. Icevis), 



which is the species here represented, has a wide geographical distribution, ranging 



from Abyssinia to the Cape ; and is characterised by its smooth skin, marked 



round the body with more or less distinctly defined tube-like lines. In colour it is 



dark brown above, and whitish beneath; some individuals being uniform, while 



others are spotted with brown on the under surface. The spur-toed frogs are 



exclusively aquatic, pursuing even their prey beneath the surface of the water, 



and capturing it with their fore-feet. The pairing-season takes place in August, 



and the large eggs are laid singly. The tadpoles, which at birth have already lost 



^their external gills, on the third day after leaving the eggs develop a pair of 



barbels hanging down from the corners of the mouth. 



