SOLID-CHESTED TREE-FROGS, 271 



The Solid-Chested Tree-Frogs. 



Family DENDROBATIDjE 



As we have already seen to be the case with the snakes, two totally distinct 

 families of frogs have taken to an arboreal life, and have thus become so like one 

 another that we have to depend on anatomical differences for their distinction. 

 In the present family, while the structure of the bones of the chest is of the same 

 solid structure as obtains in the typical frogs, and the extremities of the transverse 

 processes of the sacral vertebra are not expanded, an important difference presents 

 itself in the absence of teeth in the upper jaw and on the palate. The toes of both 

 feet are quite free from webs, and have their tips expanded into rounded discs. 

 These frogs are represented by two genera, one of which (Mantella) is confined to 

 Madagascar, and is distinguished by the tip of the tongue being notched ; while in 

 Dendrobates of Tropical America the tongue is entire. The American genus is 

 represented by seven species, among which the variable tree-frog {Dendrobates 

 tinctorius) is selected for illustration. This pretty little frog, which measures 

 barely an inch and a half in length, is widely distributed in Tropical America, and 

 is remarkable for its variability in colour ; some examples being uniformly black, 

 others grey above and black on the sides and beneath, and others grey with large 

 black blotches. This, however, is by no means the limit of variation, since some 

 examples are black above, with two or three longitudinal white or pink stripes, the 

 under-parts being grey with black spots ; while in other cases, the ground-colour is 

 black, with white spots and streaks above, and spots or marblings of the same 

 beneath. From the small size of the discs on its feet, which do not admit of its 

 clinging to upright stems, this frog seems to be less arboreal than some of its 

 allies ; and it is generally found among fallen leaves on the ground in forests. 

 Like its kindred, it displays remarkable care and attention to its young. The 

 secretion from its skin is employed by the Indians as an arrow-poison. 



The Narrow-Mouthed Frogs. 



Family ENGYSTOMATIDA?. 



An important family of the suborder is that of the narrow-mouthed frogs, 

 represented by more than a score of genera, distributed over Africa, Madagascar, 

 India and the adjacent countries, Southern China, Papua, and America. While 

 agreeing with the members of the preceding family in the absence of teeth in the 

 upper jaw, these frogs are distinguished by the broad expansion of the extremities 

 of the transverse processes of the sacral vertebra. The vertebrae are similar in 

 conformation to those of the typical frogs, and there is the same absence of ribs. 

 There is, however, considerable variation in regard to the bones of the chest, 

 several of the genera lacking the transverse bars commonly known as precoracoids ; 

 and the terminal joints of the toes may be either simple or T-shaped. Although 

 there are no arboreal forms, the family comprises terrestrial, aquatic, and burrowing 

 representatives ; the last having either the front or hind-limbs specially strength- 



