266 FROGS AND TOADS. 



in those of the hind-limb ; and the separation of the outer metatarsal bones of the 

 hind-foot by a web, the extremities of the fingers being simple or expanded. 



With the exception of the southern part of South America (where the whole 

 family is unrepresented), Australia, and New Zealand, these frogs have a worldwide 

 distribution. Although the greater majority of the species are probably aquatic 

 during the breeding-season, at other times great diversity of habit is displayed by 

 the different representatives of the genus, some being aquatic, others terrestrial, 

 and others, again, burrowing, or even more or less arboreal. The existence of 

 burrowing habits is indicated by the great development of a tubercle on the inner 

 side of the metatarsus, which in one Indian species (Rana breviceps) has a sharp 

 edge, and is used in a shovel-like manner to excavate the burrow. Such burrow- 

 ing species are further characterised by the shortness of the hind-limbs, and thus 

 assume a more or less toad-like appearance. Large discs at the ends of the toes 

 usually, on the other hand, are indicative of arboreal habits ; although, as already 

 said, smaller discs are met with in certain purely aquatic species. \*J 



Selecting some of the European representatives of the genus for 

 ' special mention, we may first notice the edible frog (R. esculenta), 

 characterised by the pointed tips of the toes, the smooth under surface of the body, 

 the presence of a broad glandular fold along the sides, and the marbling of the 

 thighs. Exceedingly variable in coloration, this frog generally has the upper-parts 

 olive or bronzy brown, more or less spotted or marbled with dark brown or black ; 

 there are generally three light stripes along the back, while the sides of the head 

 and ground-colour of the flanks are sometimes green ; the marbling on the thighs 

 occupying their hinder surfaces, and being black in colour. The males are specially 

 characterised by the presence of a globular sac, connected with the production of 

 the croaking, on each side of the head, opening by a slit behind the angle of the 

 mouth. Inhabiting Europe, Asia as far west as Japan, and North- Western Africa, 

 the edible frog is common in England, the dark race occurring in the fens of 

 Cambridgeshire, and the green variety in Norfolk. The use of the flesh as food 

 probably led to the introduction of this species into Cambridgeshire by the monks ; 

 while the Norfolk colony was imported between 1837 and 1842. From this species 

 the common English frog (R. temporia) is readily distinguished by the incomplete 

 webbing of the hind-feet, and the presence of a dark temporal spot extending from 

 the eye to the shoulder, as well as by the absence of external vocal sacs in the 

 males. Moreover, if the skulls of these two species be compared, it will be found 

 that while in the edible frog the teeth on the vomers do not extend behind the 

 line of the apertures of the posterior nostrils, they do so to a small extent in the 

 present species. In colour the upper-parts of the common frog are greyish or 

 yellowish brown, more or less spotted with dark brown or black ; the temporal 

 spot being always dark, and a light line running from below the eye to its 

 extremity ; while the sides of the body are profusely spotted, the limbs trans- 

 versely barred, and a larger or smaller number of spots are present on the under- 

 parts. This species is spread over Europe and Northern and Temperate Asia. 

 Closely allied is the moor-frog (R. arvalis), of Eastern Europe and Western 

 Asia, represented in the illustration on p. 264, which may be distinguished by the 

 tubercle on the inner metatarsal being compressed instead of blunt, and by the 



