266 
FROGS AND TOADS. 
European Frogs. 
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 (Ranct 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 liind-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. 
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 
