Acris.–The adhesive discs are very small, the tympanum is indistinct. A. gryllus, the only species, inhabits the greater part of Eastern and Central North America, extending northwards into Canada. It attains a length of 1½ inch. The coloration is very changeable, in adaptation to the surroundings. As a rule it is brown, with a more or less reddish or grey ground-tone, ornamented with dark brown or blackish irregular, longitudinal patches,one of which is bordered with light green,and there is often a light vertebral streak. The legs are cross-barred, the under parts are whitish brown and yellowish. The male has a subgular vocal sac, and its most remarkable feature is the voice, which closely resembles the noise of a cricket or of certain grasshoppers. Holbrook describes it as a merry little frog, constantly chirping like a cricket, even in confinement. It frequents the borders of pools, and is often found on the leaves of aquatic plants, rarely on the branches of such low shrubs as overhang or dip into the water. When disturbed it takes long jumps, and hides at the bottom of the pond. Insects are secured by leaps. It can easily be domesticated, and takes food readily from the hand. Sprinkling them with water never fails to make them more lively and noisy. Appearing in April in great numbers, they are said to vanish early in the autumn for hibernation. The tadpoles are metamorphosed by the end of August.

Chorophilus.–The fingers and toes are provided with very small adhesive discs. The sacral diapophyses are very slightly dilated. About seven species occur in North America, chiefly in the Southern States, one, Ch. cuzcanus, in Peru. Ch. ocularis is the smallest of the frog-kind known, and lives in South Carolina, frequenting damp places, the vicinity of stagnant pools, water-plants or low shrubs, for instance the "myrtle," Myrica cerifera. I once had two of these tiny creatures less than three-quarters of an inch in length. They were very active, and took surprisingly long leaps, jumping distances of 2 feet, but could not be kept through the winter, although they took minute insects readily enough. The head is narrow, long and pointed; the upper parts are of a rich chestnut-brown with a bronzy gloss. The upper jaw is white; a black band extends along the sides of the head and body. The under parts are yellowish white.

Ch. ornatus is another inhabitant of the South-Eastern States; its name refers to the dark brown patches on the back and sides, bordered with golden yellow, upon a reddish-brown ground-tone, while the under parts are silvery white with fine grey spots. This frog, a little more than one inch in length, lives on land in dry places, preferably in corn-fields, has no voice, and, except during the pairing season, carefully avoids the water.

Thoropa.–The fingers and toes are free, the tips simply swollen and not dilated into discs. Closely allied to Chorophilus. Th. miliaris, of Brazil, the only species, has very long toes. The head is broad and flat. The upper, nearly smooth surface of the body is flesh-coloured, with brown marblings; the limbs are cross-barred; the under parts whitish, granular on the belly. The male is devoid of vocal sacs. The total length may be 2 inches. Hensel has published the following notes of this species, under the name of Hylodes abbreviatus. The tadpoles are quite flat, their bellies forming a kind of sucking disc, so that these creatures, even before the appearance of the hind-limbs, can quickly wriggle up vertical walls of stones, provided these are covered with a little water. In correlation with this habit, the root of the tail is not compressed laterally, but is as broad as it is high, and the usual vertical fin is restricted to its distal third. On the proximal portion of the tail the ventral fin is flattened and broadened out so as to form almost the continuation of the peculiar disc-like belly. The anal opening is not a projecting tube, but is a flattened transverse slit.

Fam. 5. Cystignathidae.–This is one of the largest families, and also one of the least satisfactory. Its numerous members, more than 150, exhibit such a versatility in adaptation to circumstances (there are aquatic, terrestrial, arboreal, and burrowing species), with a corresponding development or loss of anatomical characters which we should like to rely upon as taxonomic marks, that the numerous genera not only run into each other, but also get entangled with those of other families. In fact the whole family is ill defined. It can be characterised as follows:–The shoulder-girdle is arciferous; the sacral diapophyses are cylindrical or but slightly dilated; the metasternum has either a bony style or it forms a cartilaginous plate; the terminal phalanges, although they sometimes carry adhesive discs, are never claw-shaped.

The last statement is, of course, intended to separate the Cystignathidae from the Hylidae, of which, however, the three genera Thoropa, Chorophilus, and Acris stand on debatable ground (cf. p. 186, Hylidae), while, on the other hand, most of the Australian genera, notably Chiroleptes, have unmistakably dilated sacral diapophyses. The difference from the Pelobatidae can in this case be one of degree only.

The Cystignathidae may be said to represent the Ranidae in Notogaea. Some of them can be distinguished from the true, typical frogs solely by the arciferous type of the shoulder-girdle and sternum. There is in both families the same adaptive versatility, the same amplitude in the formation of the fingertips, the occasional slight dilatation of the sacral diapophyses, the same range in the configuration of the omo- and meta-sternum. In fact, young Ranidae, before the firmisternal character is assumed, are indistinguishable from Cystignathidae, and the latter would turn into Ranidae if they could be induced to consolidate their sternal apparatus.

The geographical distribution of the Cystignathidae is suggestive of their being an old family, most of whose members have reached a high stage of morphological development. The overwhelming majority inhabit the Neotropical region, a few forms extending into tropical Central America and into the Antilles; the rest, some twenty species only, are confined to the Continent of Australia and to Tasmania.

The family name is rather a misnomer. It is taken from the genus Cystignathus, which is, or rather was, characterised by the peculiarly broadened lower jaw, hollowed out by the vocal sacs; but this generic name had to give way to that of Leptodactylus, in obedience to the often senseless rule of priority. The family is composed of three subfamilies.

Sub-Fam. 1. Hemiphractinae.–Teeth are carried by both jaws, the vomers and the palatine bones; or by the palatines and parasphenoids in Amphodus. The vertebrae are opisthocoelous, devoid of ribs, and the sacral diapophyses are not dilated. The shoulder-girdle and sternum are strictly arciferous. The omosternum is very much reduced; the metasternum forms a cartilaginous plate. The tongue is slightly free behind. The tympanum is distinct. Three genera, with eight species, all inhabitants of South America.

Hemiphractus.–The head is large; the upper surface of all the cranial bones appears pitted, owing to most of the covering skin being involved in the ossification. The temporal fossa is bridged over or roofed in by the fronto-parietal and the squamosals, so that the orbit is completely encircled by bone, as in Pelobates cultripes. The terminal phalanges are simple and are not dilated into discs. The teeth of the lower jaw are very small and numerous. The tongue is round and very small. H. scutatus, the only species, living in Ecuador and Colombia, is a frog-like creature, with a large helmet-shaped head. Total length 2½ inches.

Ceratohyla has the same kind of helmet-shaped head, and the orbit is likewise enclosed by bone, but the terminal phalanges are claw-shaped and carry regular adhesive discs. This genus, the five species of which live in Ecuador, bears undoubted resemblances to the Hylidae. In C. proboscidea the upper eyelid is produced into a little upright fold, as in Amphignathodon and some species of Nototrema and Ceratophrys among Cystignathidae. The snout is produced into a long, compressed, bifid appendage, and the heel carries a triangular flap. In C. bubalus the partly ossified helmet sends out a pair of diverging processes, formed by the squamosals, extending backwards and sideways from the concave and ridged interorbital spaces. The tip of the snout and the tips of the divergent horns form an equilateral triangle, and the whole head bears a striking resemblance to some of the fossil Reptiles from the Elgin Sandstone, e.g. Triceratops. Total length 3 inches.

Amphodus wucheri.–The only species of this genus has been found near Bahia. It has teeth on the palatine bones and five series of small teeth on the parasphenoid, but none on the vomers. The teeth of the mandible number about eleven on each side and decrease in size towards the symphysis. The tympanum is distinct; the heart-shaped tongue is free behind. The cranial bones are only slightly pitted. The skin is smooth above, chocolate-brown, spotted with yellow, and with a yellow band on the sides of the body beginning with the upper eyelid and ending in a broad patch above the vent. The under parts are yellowish white.

Sub-Fam. 2. Cystignathinae.–The upper jaw alone is provided with teeth. Vertebrae procoelous. The twenty-seven genera of this sub-family have been arranged in the following key, merely for convenient determination.

Pseudis, widely distributed over South America, consists of four species which have the appearance of long-legged frogs. The fingers, of which the first is opposed to the others, are free; the long toes are fully webbed. The tympanum is exposed.

P. paradoxa is absolutely aquatic, floating in pools, and is extremely shy. In life it is most beautifully coloured with bronze, bright green, and black markings above; underneath it is shiny yellow, with brown spots on the body and stripes on the thighs. Within a few minutes after death all the brilliant colours of the smooth skin of the back turn into dull uniform brown, with indistinct darker spots. Total length of the adult from 2 to 2½ inches. The specific name refers to the peculiar shape and monstrous size of the larva or tadpole.

One of the larvae described and figured by Parker measures 10⅓ inches in length, the head and body taking up 3⅓ inches. The spiracle lies on the left side and the hind legs are ½ inch long, just breaking through the skin. The vent is median. The huge tail is very thick and muscular, and is furnished with a high, irregularly shaped dorsal and ventral fin, the whole organ measuring 4 inches dorso-ventrally. Another larva, or rather tadpole, in the national collection is older, and although still very large, namely, 7 inches long, has fully developed hind-limbs 3 inches long; the fore-limbs are less than half that size, the left protrudes through the spiracle, while the right has broken through the skin. The dorsal and ventral fins of the tail have much shrunk; the whole organ, 5 inches long, is gradually tapering to a point like the tail of ordinary tadpoles. By the time that the tadpole is nearly ready to leave the water, its whole bulk is reduced to less than one-fifth that of the largest tadpole. It measures from snout to vent only 1½ inch (in the 7-inch tadpole this distance is fully 2 inches), and the tail, devoid of fins, is reduced to 2 inches in length. Instead of the solitary left spiracle there are now two, one on the ventral side and a little in front of the base of each arm, the border of each hole being continued by a peculiar semilunar fold.

Hylodes.–The numerous species, nearly fifty, of this tropical American genus exhibit several anatomical differences. The tympanum is sometimes indistinct or hidden, in which case the Eustachian tubes are generally very narrow. The fingers are free, and carry discs, like the toes, which are sometimes slightly webbed. The males have a subgular vocal sac, producing a loud, or whistling, voice. The general appearance is that of land- and tree-frogs; the size is small, mostly between 1 and 2 inches.

H. martinicensis is about 1½ inch in length. The ground-colour is pale yellow-grey, with a large brown patch on the nape, which colour is continued over the back in the shape of more or less coherent or dissolved patches. A dark brown stripe runs along the middle of the sides. The limbs are barred with brown, the under parts are whitish. This species, known by the vernacular name of "coqui" inhabits many of the West Indian islands, e.g. Barbadoes, Martinique, Porto Rico, and Hayti. It has become famous, as it was the first instance known of a frog which undergoes its whole metamorphosis within the egg. The pairing takes place on land, in the months of May and June, when the female lays about twenty eggs, which are enveloped in a foamy mass and glued on to a broad leaf, or hidden in the axillae of Iridaceous plants. The mother seems to remain in the neighbourhood watching the eggs, which are large, measuring 4-5 mm. in diameter. Dr. Gundlach, a resident in Porto Rico, was one day, in the month of May, attracted by sounds like those of a young bird, and found three males and one female of this species sitting between two large leaves of an orange-tree. He put them all into a glass vessel and soon saw a pair in embrace. The female laid about twenty-five pale straw-coloured eggs. The embryo develops neither gills nor gill-openings, but a large well-vascularised tail, by means of which, being immersed in the watery fluid contained within the egg, it seems to breathe. After twenty-one days the tadpole, having used up all the available yolk and fluid, and most of its own tail, bursts the egg-shell and hops away as a little frog of 5 mm. in length, but still with a stumpy white tail, which is quite absorbed within the same day.

This species has several times made its appearance in the tropical houses of Kew Gardens. It seems to have bred and vanished again.^[92]

Calyptocephalus is remarkable for the dermal ossification of the cranium, which has assumed the greatest possible extent. It affords a curious parallelism to Triprion and other Hylidae, which are likewise Central American forms. Only two species are known; C. gayi of Chili, and C. testudiniceps of Panama. They are large, thoroughly aquatic creatures, 5 to 6 inches in length, with huge heads. The tadpoles grow to an enormous size. One specimen of C. gayi in the National Collection is more than 6 inches in length, the tail taking up more than half of the total: the spiracle lies on the left side, the vent on the right, and the hind-limbs are still half enveloped in a kind of fold of the skin.

Ceratophrys is a genus of some ten toad-like species, living in South America, from Guiana to Argentina. The generic name alludes to the peculiar modification of the eyelid, which in most species is developed into a triangular, upright, but flexible appendage. The head, in conformity with the huge mouth, is very large. The tympanum is rather indistinct, sometimes quite hidden. Several of the species have a large dorsal shield, which is produced by a thick ossification of the cutis, but is not fused with any of the vertebral processes. The male has a vocal sac. C. dorsata s. boiei of equatorial Brazil is a monster toad, reaching a length of 6 inches. The upper eyelid is transformed into a triangular horn, whence a cutaneous ridge extends all along the side of the back, meeting that of the other side above the vent. There is no osseous shield on the back. The tympanum is hidden. Ground-colours, orange or green, with sharply marked dark brown or blackish patches.

C. cornuta, in Northern Brazil, lacks the dorsal shield, but has horned eyelids and a visible tympanum. Its coloration renders it one of the most beautiful toad-like creatures known. The ground-colours are green, black and brown, with an orange-yellow stripe over the head and back. All these colours are most pleasingly blended and arranged in marbled patches or stripes radiating from various centres, as, for instance, from the eyes towards the circumference of the mouth, the slit of which they pass, the same line of the pattern being continued upon the lower jaw. The whole surface makes the impression of a gay but exquisitely harmonious carpet. The under parts are yellow, inclining to white towards the middle.

C. ornata has a dorsal shield. The tympanum is just visible, and the eyelids form only low but sharp-edged projections. This is likewise a beautiful toad, living chiefly in Uruguay, Northern Argentina, and Paraguay, where it is universally known as the "escuerzo," one of the Spanish words signifying a toad. Its size rarely surpasses 4½ inches. The ground-colours are greenish and yellow, with large dark green patches on the back, decreasing in size on the flanks.

Each of these insular patches is surrounded by a narrow line of white and yellow dots, interspersed here and there with lines of rusty brown or red. The object of this elaborate carpet-like pattern is concealment. These toads–and this applies to all the species,–bury themselves half in the ground, preferably in the grass, where they are well-nigh invisible. If there is not enough green vegetation, they throw, with their feet, little lumps of earth upon their backs, the skin of which becomes at the same time more crinkled and assumes duller tones. There the creature lies, perfectly concealed, betrayed only by the metallic glittering eyes, waiting for some unfortunate creature to pass into the trap represented by the enormous mouth, which opens and shuts with lightning-rapidity and with an audible snap. They seem to live chiefly on frogs, and sometimes they turn cannibals. Two specimens were brought over to me from Buenos Aires by a friend, in a well-closed basket with moist soil at the bottom, but only one was visible on arrival. The other was inside the larger one, and could still be felt through the soft body. This same cannibal took large-sized frogs greedily, one or two for a meal, swallowing them whole and then sinking back into its lair, which it scarcely ever left, except for an occasional soaking bath in its water-pan, especially before shedding its skin. It lived for many months in the same enclosure with a pantherine toad, Bufo mauritanica, of equal bulk, until one morning I found the Moroccan half swallowed and almost lifeless in the mouth of the American, whence it was rescued with difficulty. It came round after a few hours, but never fully recovered, lingering on for weeks; the skin was changed to a lead-colour so far as it had been swallowed and partly dissolved by the gastric juices, and soon began to develop festering ulcers.

These "horned toads" make a squeaking noise when teazed, not at all loud or strong in proportion to their size. Ill-tempered individuals jump at their aggressor and can inflict rather painful nips. They hibernate during the dry season in the ground.

Lepidobatrachus.–Large teeth in the upper jaw, and two large tooth-like projections in the lower jaw near the symphysis. Vomer toothless. Sacral diapophyses not dilated. Tongue round, and free behind. Tympanum distinct. Great development of the membrane-bones on the head, and a weaker ossification in the skin of the back, recalling that in Ceratophrys. The eyes are closely set together, and the nostrils take up the most elevated portion of the head. Pupil horizontal. The two species of this genus were discovered by Budgett^[93] in the Paraguayan Chaco. L. asper lives continually in muddy pools, floating with just the eyes and nostrils above the surface. If disturbed it slowly sinks to the bottom, leaving no ripple. It feeds largely on Bufo granulosus. Total length from about 3 inches. The skin of the upper parts is tubercular, tough, and of a dull leaden colour; the tips of the toes are horny. L. laevis is smooth and slimy, "with the organs of the lateral line showing clearly upon it," a feature elsewhere known to exist in Xenopus and Leptobrachium only.

Leptodactylus = Cystignathus.–Some twenty species inhabit tropical America, from Central Mexico to Buenos Aires. The fingers and toes are not webbed and end mostly in points; only a few species, e.g. L. hylaeodactylus, having small adhesive discs. The legs are long and the general appearance is very much like that of an ordinary frog.

One of the commonest and prettiest Brazilian species is L. ocellatus, which is characterised by a number of longitudinal glandular folds on the back and flanks. The colour of the upper parts is olive-brown, that of the prominent folds is yellowish white, interspersed with black spots. The under parts are yellowish white, with blackish marblings on the throat. The males have a sharp black spur on the inner carpal edge and one on the rudiment of the thumb. Total length about 4 inches.

According to Hensel^[94] the spawning takes place in Rio Grande do Sul after hibernation. The voice of the male is then very loud, resembling the sound made by a carpenter chopping a beam. They repair to ponds and produce a cup-shaped puddle, about 1 foot in width, by raising a wall of mud, which separates the inner water from that of the pond. The tadpoles remain in this nursery until the spring-rains demolish it and set the young ones free. Drought causes the drying up of these water-pans and subsequent destruction of the brood.

L. mystacinus is another Brazilian species, about 2 inches in length. Its specific name refers to the dark brown stripe which runs from the tip of the mouth through the eye to the tympanum. This species is thoroughly terrestrial, and never enters the water. It digs a cavity, the size of an ordinary tea-cup, under stones or rotten trunks, always in the neighbourhood of ponds and just so high above the water that the latter can rise up to the nest in the rainy reason. The straw-coloured eggs are laid in this cavity, and are enveloped in a foamy, sticky mass, like the well-beaten white of an egg. The young tadpoles seem to live on this froth until the rains set them free. When, however, the rains delay and a drought kills the broods of other less circumspect species, these tadpoles, still provided with gills and long tails, remain in their moist nest or withdraw further beneath the rotten stumps, huddled together in large numbers until the next rainy season.

Similar nursing habits have been recorded of L. albilabris, which inhabits Mexico, Cuba, and several other West Indian islands. The same applies to L. typhonius. Gundlach found eggs of this "Sapo" in Puerto Rico on the 4th of November; on the 25th the young showed the first signs of hind-limbs, on the 3rd of December of fore-limbs, and on the 7th of the same month they began to climb out of the water.

Paludicola is a semi-aquatic genus with some eighteen species, ranging from Mexico to Patagonia and across the Andes into Chili. Some of them have a peculiar gland on the lumbar region, or large, flat warts on the back, sometimes arranged in longitudinal folds. The toes are slightly webbed, or free, according to the more or less pronounced aquatic habits.

P. fuscomaculata, an inhabitant of Southern Brazil, Paraguay, and Uruguay, is a short-limbed frog, with spreading slender toes and a small head. There are shovel-shaped, black, horny tubercles on the metatarsus. The general colour is olive above, with darker markings and confluent white-edged spots; the limbs are cross-barred; the lumbar glands are black, with a white margin in front. The male has a vocal sac. Budgett^[95] gives the following account of its habits:–

The peculiar cry, which is so constantly heard in the neighbourhood of shallow pools in the Paraguayan Chaco, and resembles that of a kitten, is produced by the alternate inflation of throat and abdomen. When fully inflated, the frog appears to be the size of a golf-ball, but, if startled, instantaneously shrinks to one-fifth of that size, so that it seems to have vanished. It has also the power of ventriloquising. The food consists largely of water-beetles. In the spawning time it was found at night floating on the surface of pools in the distended condition, and crying to the females in a most mournful way. On coming to the surface it fills its lungs with a few gasps, greatly distending the walls of the abdomen, and then drives the air into the vocal sacs, causing them to become distended as the body collapses, and giving rise to a kitten-like cry.

The eggs are chiefly laid in January, and are found embedded in a frothy mass floating upon the surface of the water. The eggs measure only 1 mm. and are without pigment, and with extremely little yolk. The larvae become free-swimming within from eighteen to twenty-four hours after the first segmentation. When ready for hatching they wriggle their way through the froth to the water below, and hang into it from the floating froth.

P. biligonigera s. notata, in Brazil, lacks the lumbar gland, the place of which is marked by a black spot. The upper parts are olive, with darker marblings and a dark lateral stripe. The male has a black throat and two external vocal sacs. Hensel found the eggs, in Rio Grande do Sul, in September, forming a frothy mass of the size of a fist, floating between grass upon the water near the margin.

The following three genera may serve as Australian examples, especially since we are indebted to Baldwin Spencer for interesting observations made on their habits in Central Australia.^[96]

Chiroleptes, of which six species are known, is easily recognised by the first finger, which is opposed to the others. The sacral diapophyses are slightly dilated. The general shape is that of a thick-headed, rather stout land-frog or of a tree-frog. The tympanum is distinct, and the toes are only half webbed, or even less, except in Ch. platycephalus, in which the toes are entirely webbed and the tympanum is indistinct. This species is about 2 inches long, uniformly olive-green above, with a few tubercles on the otherwise smooth skin. Other species rather resemble the European Natterjack in coloration.

Spencer's account is as follows:–"In Central Australia Ch. platycephalus seems to prefer the hard clay pans rather than sandy creeks, as the sand-beds of the latter are too loose for the formation of the burrow. We came across the animal first when encamped by the side of a very shallow clay pan, the floor of which was deeply cracked with the sun's heat. Around the edge were withered shrubs of Chenopodium nitrariaceum, and it was at the base of these that the black fellows looked for the burrow. In the hard-baked clay were imprints made by the frog as it burrowed, and about a foot underground we came across the animal, puffed out into a spherical shape, and just filling up a cavity, the walls of which were moist but not wet. The ground was so hard that it had to be chipped away. When one side of the burrow was opened, the frog remained perfectly still; its lower eyelid was drawn up over the eye and was very opaque, giving rise to the belief amongst the blacks that the animal is blind. In the sunlight, after a short time, it opened its eyes.

"On squeezing the body, water was forced out of the cloaca; this was accumulated principally in the urinary bladder. On cutting the body open it was seen that there was a certain amount of water in the subcutaneous spaces, but that the greater portion, which caused the great swelling-out of the body, was contained in the body-cavity itself; and it was also observed that the lungs were considerably distended and lengthened, their apices lying right in the pelvic region. They contained air and not water, but their outer faces were bathed with the water in the body-cavity." The larvae and tadpoles probably develop with extreme rapidity, soon to aestivate as very small frogs.

Heleioporus has a calcified metasternal plate and slightly dilated sacral vertebrae. The two species have a toad-like appearance, owing to their stout bodies, short limbs and conspicuous parotoid glands. H. albopunctatus is mottled whitish red and brown above; it extends from Western into Central Australia. H. pictus is olive, with darker marblings, and is distinguished by a light vertebral line. It is likewise found in Central Australia, and it extends into Victoria and New South Wales. Spencer found it in swarms after heavy rains, the specimens being much swollen and distended with caterpillars and beetles. They looked as if they were simply gorging themselves with food preparatory to returning again to their long aestivating condition.

Limnodynastes is one of the commonest genera in Australia. The six species have the habits and appearance of stout frogs or smooth toads. L. dorsalis seems to range through the whole of Australia, from east to west, and looks like the European Pelobates. The skin is smooth, but with an elongated white gland extending from beneath the eye to the shoulder, and another glandular complex on the thigh. The upper parts are mottled olive-brown, often with a light vertebral line. The under parts are whitish, with brown spots. The male has a vocal sac. One of the specimens in the National Collection contained a half-grown Heleioporus albopunctatus in its stomach.

Concerning the pairing and the other habits of the Anura of New South Wales we have some valuable notes by J. J. Fletcher.^[97] He observes that Australian frogs spawn whenever they are ready, and when the very irregular conditions of moisture will allow it, but that they are not all ready at the same time, i.e. they have no fixed period of the year. Limnodynastes, Hyla aurea, and H. coerulea deposit their spawn in the water, in more or less irregular floating patches, which look white and frothy. The period extends from July to May, and is at its height in August and September; but if there is a spring-drought vigorous spawning may be looked for about the middle of January, when heavy showers are likely to occur. Crinia and several Hyla, e.g. H. ewingi, spawn at any time of the year. The eggs form small submerged bunches, enclosed in a transparent jelly, attached to the blades of grass or twigs of dead branches in the water.

Pseudophryne, a genus closely resembling Crinia, but on account of the absence of teeth in the lower jaw relegated to the Bufonidae, spawns during the Australian summer and autumn. The numerous ova of P. australis and P. bibroni are laid separately, not in the water, but under stones, or in the débris of reed- and grass-tussocks, on the edge of a pool.

The larvae of Pseudophryne and others have often to depend upon the next following rain, sometimes waiting for months to be released from the eggs, wherein they have so far developed. But the tadpoles, once hatched, probably do not bury themselves; they either metamorphose or die.

The males of Mixophyes and Hyla, grasp the females in the axillary region; those of Limnodynastes, Hyperolia, Crinia, and Pseudophryne throw their arms round the inguinal or lumbar region.

For some three months during the winter, commencing about May, the frogs, like lizards and snakes, resort to shelter under logs and stones, beneath which they are then to be met with in a more or less sleepy condition. During the hot and very dry periods many bury themselves in the drying-up mud, which becomes very hard, and does not release them until the next rains. They croak during showery times of the year. There is no evidence that any Australian species live in the high Eucalyptus-trees.

Hylopsis platycephalus, of South America, is of importance as forming a link with the Dendrophryniscinae, owing to the very small size of the teeth in the upper jaw. There are no vomerine teeth. The fingers and toes are webbed, and furnished with discs. The very small omosternum and the metasternum are cartilaginous. The pupil is horizontal. Total length, about or under 1½ inch.

Sub-Fam. 3. Dendrophryniscinae.–The two Neotropical genera of this sub-family are characterised by the entire absence of teeth. The toothless condition of the upper jaw is really the sole character which separates them from the Cystignathinae, taken as a whole. The suppression of the tympanum and of the Eustachian tubes in Batrachophrynus, and the fully webbed toes of B. macrostomus indicate complete adaptation to aquatic life. The absence of the omosternum in Dendrophryniscus, the absence of vomerine teeth, the dilated phalangeal tips, the entire and quite adherent tongue, are all features which likewise occur in some of the Cystignathinae, and therefore cannot be urged against their affinity. Lastly, the recently discovered South American genus Hylopsis is, as pointed out by Werner,^[98] an intermediate link, owing to the extremely small, scarcely visible teeth in the upper jaw.

Dendrophryniscus brevipollicatus has been found in the neighbourhood of Rio Janeiro. The head is depressed and triangular. The tongue is entire, but free behind. The tympanum is suppressed. The omosternum is absent; the metasternum forms a long bony style. The sacral diapophyses are cylindrical. The terminal phalanges are simple, but carry dilated tips. The first finger is rudimentary. The skin is nearly smooth, reddish brown above, whitish below; the limbs are cross-barred.

Batrachophrynus inhabits the mountains of Peru. The head is much depressed and small, with the eyes directed upwards, as is usual in essentially aquatic species. The tongue is large, circular, and entirely adherent. The tympanum and the Eustachian tubes are suppressed. The omosternum is cartilaginous, and the metasternum forms a cartilaginous plate. The sacral diapophyses are cylindrical. The terminal phalanges are simple, and carry no discs. The four fingers are short; the toes are webbed. The male has no vocal sac. B. brachydactylus has a smooth skin, olive-brown above with darker spots. B. macrostomus, 2 inches in length, is distinguished by its larger size, and by its completely webbed toes.

Fam. 6. Engystomatidae (Narrow-mouthed Toads).–Firmisternia with dilated sacral diapophyses.

Sub-Fam. 1. Engystomatinae.–Without teeth in the upper jaw.–Although there are only about 60 species known, these have been grouped into more than two dozen genera, many of which are represented by one or two species only. The range of this sub-family is peculiar, namely, Neotropical and Palaeotropical. Scaphiophryne and Rhombophryne are peculiar to Madagascar; Calophrynus occurs in the same island and in the Indian region; Xenobatrachus, Sphenophryne, Liophryne, Mantophryne, Callulops and Xenorhina live in New Guinea. Breviceps, Cacosternum and Hemisus are confined to Africa, while of Phrynomantis two species live in Africa, and the third in the Malay island of Amboina. Such freaks of distribution indicate either that many of these genera are not established upon very valid characters, or that their respective species are instances of convergent evolution, and do not form natural genetic groups.

Many of the members of this sub-family live upon ants and termites, and it is a well-known fact, not restricted to the Anura, that this kind of fare has a peculiar, modifying influence upon the structure of the mouth, teeth, tongue, limbs, and various other organs. In the present case the tongue is not much affected; it is, with few exceptions, more or less oval, not nicked, but free behind; in the Indian Glyphoglossus and in Rhombophryne of Madagascar only is it modified into a rather long and grooved, almost double, apparatus.

A very common feature is the small size of the mouth and the formation of a snout, which projects beyond the upper rim of the mouth and beyond the nostrils. Such a prominent and pointed snout is well developed in Rhinoderma, Phryniscus, Calophrynus, Stereocyclops, Hypopachus and Engystoma. The mouth is very narrow in Cacopus, Glyphoglossus, Breviceps, Rhombophryne, and Hemisus, all creatures which seem to be confirmed eaters of ants and termites. However, it must not be supposed that the mouth of all the genera is narrow, although this character, rather marked in Engystoma, is now embodied in the name of the family. A peculiar development of the palatal region is possibly correlated with this food. The palate is mostly toothless, but its skin is frequently raised into a transverse fold, between or behind the vomers, and into a second fold in front of the oesophagus; these folds are sometimes rather hard and serrated or denticulated. The palatine bones carry true teeth in Rhombophryne, and sometimes in Callula; in Xenobatrachus the teeth are reduced to two large pairs. The tympanum is usually hidden.

The shape of the body is generally very stout. The limbs are short, notably so in Glyphoglossus, Breviceps, Rhombophryne, Hemisus, Stereocyclops and Cacopus. Others, for instance most species of Microhyla, Phryniscus, Callula, and Sphenophryne, are of a very slender build; and their limbs, instead of being short and well adapted to digging, are long and may even be provided with typical adhesive discs, supported by T-shaped phalanges, especially in the two genera last named, and in Scaphiophryne and Phrynomantis. However, none of the forms provided with discs are known to be arboreal.

Exceptional diversity is shown in the shoulder-girdle and sternum. The omosternum occurs only in Rhinoderma and Hemisus. The metasternum is a cartilaginous plate, very large in Cacopus, distinctly small in Breviceps, and almost absent in Hemisus. The precoracoids and clavicles show all stages from a well-developed condition (Breviceps, Rhombophryne, Hemisus, Rhinoderma, Phryniscus and Brachycephalus) to complete absence. The circumstance that these bars are very weak in Melanobatrachus, Calophrynus, Scaphiophryne and Hypopachus, i.e. in Palæo- and Neo-tropical genera, indicates a widespread tendency towards complete suppression, a feature independently aimed at both in America (Engystoma) and in the Old World.

Until we know something about the habits of the members of this much diversified sub-family, it is idle to connect the various modifications with each other, and thus, by correlation, to find out their meaning. Those forms which possess well-developed discs on their fingers and toes are said not to be arboreal. What is the true meaning of the prominent snout which is not restricted to the digging forms? Most of the good diggers have well-developed precoracoid bars, and the coracoids are distinctly strengthened, but in Glyphoglossus and in Cacopus the precoracoids are entirely absent, and this loss is compensated for by exceptionally strong coracoids.

On the whole, those genera are to be considered as the most primitive which have undergone the fewest losses. Those with a complete shoulder-girdle, with an omo- and meta-sternum and with simple phalanges, are necessarily the older forms. One step farther back in another direction, the possession of teeth on the palate, and on the upper jaw, leads to those genera which have been separated off as Dyscophinae, while teeth in the lower jaw constitute the Genyophryninae. Lastly, the firmisternal type has necessarily been evolved from the arciferous condition, and there the two Bufonid genera Myobatrachus and Rhinophrynus, the former Australian, the latter Mexican, with their narrow and scarcely overlapping epicoracoid cartilages, seem to form a connecting link, although their ant-eating habits, with concomitant modifications in structure, may be nothing but cases of convergent evolution.

Key to the genera:–