hind feet; these have the great toe united, and the two next united as far as the nail, in such a manner that we seem at first sight to see only two toes, of which the inner has two nails. These animals walk upon two feet; and by the help of their tail, which is long and stout, maintain themselves in an erect position; in form and habit they resemble the kangaroos, from which they differ in having a canine tooth in the upper jaw. Their food is frugivorous; they possess one large stomach divided into pouches, and garnished about with enlargements; cœcum of a moderate size and round. We are acquainted with only one species, which is about the size of a rabbit, and of a mouse color, whence they have been called kangaroo rats. Natives of New Holland: the aborigines call them Potoroo. Group. 2. Canino nullo.

This group differs from the third only in the absence of canine teeth.

Gen. Macropus of Shaw.-The kangaroos. These exhibit all the characters which we have assigned to the kangaroo rats, except in the aforementioned canine tooth in the upper jaw, and in their mean incisors not being separated at a distance from each other. The inequality of the legs is still greater, so that they cannot walk upon four feet but with pain and difficulty, but spring upon the hind feet with great force. The thick nail upon the middle toe behind, which nearly resembles a hoof, serves them for a defence, as they can rest their weight upon one leg and their enormous tail, and give a violent blow with the free foot. In other respects they are animals of a mild disposition, and live in flocks. Their grinders present nothing but small risings. There are five, but the anterior often falls out by age, which makes them seem to have only three. The stomach is shaped like a long pouch, divided into two enlargements, like the colon; cœcum is large and swollen; radius allow the forearm a complete rotation.

Great kangaroo. Macropus. Didelphis gigantea. Sometimes attains the height of six feet, and is the largest animal in New Holland : first discovered by Cook, and now propagated in Europe. It is said that the flesh resembles that of a deer. Their young ones at their birth have but one thumb, and retreat to the pouch of the dam, till age has fitted them for sustaining themselves. It is by thrusting their muzzles out of the pouch that they receive the food from her. They live in herds under the conduct of the old males; they take exceedingly long leaps; it would seem that many species are confounded under this name. Color gray with lighter shades.

Elegant kangaroo. Macropus elegans. About the size of a hare, light-gray, striped with brown across the body. From St. Peter's Island.

Kangaroo d'Arve. Didelphis brunii of Gmelin, called philander d'Arve or lapin d'Arve, by the inhabitants of Amboyna; but the naturalists of Europe have not paid sufficient attention to the description which Valentine and Bruyn have given. About the size of a hare; brown above, tawny beneath; it is found in the island of Arol near Banden, and in the island of Salor, and has long been known to the students of natural history.

Group. 3. Pare incisorum infra. Has the lower jaw with two long incisors, but without canine teeth; the upper jaw has the middle incisor long, and some small ones on each side, with the canine teeth.

Gen. Drazimenus.-Sine cauda. Koala. Has

the body short and thick, without any tail; four toes before divided into two separate pairs; the thumb and the index in one pair, and the rest in the other; this conformation renders their forefeet very proper for seizing and grasping; hind foot destitute of the thumb, next toes to it united like the preceding group. We are acquainted with only one species, the hair of which is of an ash color. This animal passes one half of its life upon trees, and the other burrows which hollows with its foot; the dam carries her young one a long time upon her back.

Group 4. Dentibus glirium.

Gen.. Phascolomys of Geoffroy.-If we regard the teeth and intestines we must place these animals among the rodentia, but the articulation of the lower jaw permits us to assign them to the carnivora, which we choose to do, because we have been led to them by descending in an uninterrupted series from the didelphis to the phascolomys. Besides the male organs of generation have a perfect similarity to those of the marsupial animals. They are stupid creatures; their head is flat and their legs short; body loose and without tail; fore-feet with five nails, and four with a small tubercle in place of a great toe behind; all fitted for burrowing in the earth. Rate of progression excessively slow. Two incisive teeth in each jaw, long, and nearly equal to those of the rodentia; the grinders have each two risings across their surface; feed upon herbs; stomach shaped like a pear; cœcum short and thick, furnished as in man with a vermiform appendage; male organ of generation forked, as in the opossums. One species only known, about the size of a badger; hair copious, of a color more or less yellow. From King's Island, south of New Holland. Live in burrows. Propagate among us. The flesh is reputed to be excellent.

Didelphis ursina. Wombat.

ORDER IX.-RODENTIA.

Rodentia, to which we are come from a contemplation of the phalangers, in which the canine teeth were so small that they might have been ac counted as nothing; and the food, consisting entirely of vegetables, seemed in reference to economy to separate them completely from the carnivora. Their intestines we observed to be long, and their cœcum ample. In the kangaroos we noticed the total absence of canine teeth, and a diet like the phalangers. We might, indeed, have begun with the phascolomys, but since we found it expedient, in an arrangement, to fix the vanishing points somewhere, we could not do this without encroaching upon the precincts of what we laid down to be the chief and unvarying characteristic of the carivorous order, namely, the hinge-like articulation of the lower jaw. The rodentia have two large incisors in each jaw separated from the grinder by a void space; they cannot, therefore, easily seize their prey, nor tear flesh, neither cut the food, but only by continued labor reduce it to very small par ticles, or, in one word, gnaw it. Whence a verbal noun derived from rodo, alluding to the peculiarity above-mentioned, becomes a very appropriate denomination for an order of animals, which, since their business and pleasure seem to consist in gnawing, may, in an eminent manner, be called animalia rodentia. In this way they will attack the hardest substances, and ofttimes nourish themselves on wood and bark; for

the better fulfilment of this purpose the incisors have no enamel but on the forepart, so that their posterior edge, wearing faster than the anterior, they always appear slanting upwards. We cannot forbear calling the attention of the reader aside to admire the simple process which nature has contrived for keeping these teeth always sharp. To preserve this prismatic form, an increase at the root is necessary corresponding to the quantity worn away by attrition, which is so considerable, that, if one of them chance to be lost or fall out, the one opposite, having nothing to wear it down, is developed so much as to become monstrous, and will, if the animal be kept alive by the introduction of food into its mouth, through the opening left between the incisors and grinders, nail the lower jaw to the upper. The lower jaw is articulated by a longitudinal condyle, so as to be capable of a horizontal motion, backwards and forwards, to suit the action of gnawing; the molar teeth are crowned with plates, of which the eminences of enamel are always alternate, in order that they may be in opposition to the horizontal motion of the lower jaw. The genera in which these eminences are in simple lines, and where the crown is plane, are exclusively frugivorous; those in which the eminences are replaced by flat tubercles are omnivorous, but those animals of this order which are furnished with grinders, and armed with a few points, attack other animals more readily and approximate to the carnivora. The form of the body is such as to make the hind parts preponderate, hence it comes to pass that in progression they leap rather than walk. This conformation, in some of the genera, is found as excessive as it appears in the kangaroos. The intestines of the rodentia are very long, stomach simple, or somewhat divided; the cœcum is sometimes more voluminous than the stomach, nevertheless in the genus musoreus this intestine is wanted. In the whole of this order

the brain is almost smooth and without convolutions; the orbits are not separated from the temporal fosses, which have some depth; the eyes have a lateral direction; the zygomatic arches, being thin and bent down, indicate the weakness of their jaws; the fore-arm is susceptible of a rotatory motion, and the two bones are often united into one. Finally, the inferiority of these animals betrays itself in almost all the details of their organisation, though the major part of the genera have strong clavicles, enjoy a certain hability of address, and make use of the fore-paws in applying the

food to their mouths.

Division I.-CLAVICULIS PERFECTIS. Gen. Castor of Linné.-Caudâ planâ, rotunda ambitu, squamis, que abductu. The beaver is distinguished from all the rest of the rodentia by its tail, which is flattened horizontally, almost of an oval form and covered with scales. Five toes on each foot, those behind united by membranes, the one next the great toe has a double nail placed in an oblique direction. Grinders, in number four, having the appearance of a riband folded upon itself in such wise that they reem one notch on the inside and three on the outside in the upper jaw, but inversely in the lowest.

Castor fibra, common beaver. All the rodentia are provided with clavicles which cannot be discriminated by any external sensible mark, nor do the long incisive teeth in the lower jaw always furnish the naturalist with unvarying and well-defined

differences for distinction. But we must, for the sake of a perspicuous order, separate, as we do, the mole-rats and the helamys or jumper; the others allow themselves to be divided by the grinders.

Subdivision 1. Molares ex laminis structe. Those which have their molar teeth prismatic and formed by the repeated superposition of enamel plates; a sort of structure which we find in the hares and even in the elephants.

Meadow mice; mures auricolæ. All the known ones have three grinders throughout, each formed of five or six and sometimes seven triangular prisms ranged alternately in lines.

Gen. 1. Fiber of Cuvier.-Caudâ longa atque mated feet and long compressed tail covered with compressâ. Ondatras. Field mouse, with palscales. Only one species known.

Musk rat of Canada. zebethicus of Gmelin.

Castor Tibethicus. Mus

Gen. 2. Hypudeus of Iliger.-Arvicola of Lacipede. Cauda pilis vestitâ. Common field mouse. Tail clothed, nearly as long as the body

Mus amphibius, water-rat.

M. arvalis of Linné. About the size of a common mouse, tail somewhat shorter than the body. M. œconomus, or economic mouse of Pallas.

Gen. 3. Georychus of Iliger.-Lemmings of Cuvier. Caudâ auribusque curtissimis. Tail and ears very short; toes before peculiarly adapted for burrowing. The following species have five nails very distinct upon the forefoot.

Lemming. Mus lemnus of Linné. Tocor. Mus appalax of Gmelin. Lemming of Hudson's Bay. Mus Hudsonius. Subdivision 2. Molares radicibus manifestis. base into roots, but the flat crown presents the transRats grinders, which divide themselves at the verse lines of increase. Frugivorous.

Gen. Loncherites of Iliger.-Pilis in spiculas traductis. Echemys of Geoffroy. Has four grinders throughout, which present severally four transverse plates (in the lower jaw) united in pairs; in the upper jaw they present respectively three, of which two are united. They are American animals, with a shape nearly like mice, and lengthened as those of rats; hair very often flattened, enlarged, stiff, and terminating in a point.

Gilded tail. C. echemys chrysurus. Hystrix chrysurus of Schroeber.

shorter than the body. Found in Cayenne and E. spinosus of Azarra. As large as a rat; tail Paraguay, subterranean woody burrows.

Myoxus of Gmelin, dormouse loir. Has also but their hair is soft and their tail clothed and four grinders entirely divided by transverse bands,

the rest by their hind feet being palmated two thirds; their grinders have a peculiar character in that they have the crown obliquely quadrangular or rhomboidal, which is hollowed in the middle like a spoon. Aquatic.

Hydromys leucogaster of Guiana. We are of opinion that we might refer hither an animal of which the skin comes to the central parts of Europe for the use of hatters. Its anatomical structure is not well examined.

Quoaigu of Azarra. Mus crypus of Molina. Gen. 2. Mus of Cuvier.-Cauda longa squamis obtecta. Rats, properly so called. Have three grinders in each side respectively, with flat tubercles, of which the fore one is larger than the rest; tail long and scaly. Species very numerous, too well known by their fecundity, and the havock they make in our wardrobes and promptuaries.

Common mouse. Mus musculus. Common rat. M. rattus, of which the ancients take no notice, and it appears to have penetrated into Europe in the last age. Cuvier.

Surmulot. M. decumanus. Arrived in Europe in the sixteenth century, and is now more common in Paris and in some other towns than the other species.

M. caraco of Palla. Tail somewhat shorter; grinders very strong, of a flaxen color; found in Tartary.

M. cahirinus of Geoffroy. Spines instead of hairs upon the back. It is mentioned by Aristotle.

M. sylvaticus. Hair red, in other respects differs not from the common house mice.

Gen. 3. Cricetus of Cuvier.-Cauda brevi pilis vestita. Hamsters. Teeth like those of the rats proper; tail short and clothed with hairs; in each side of their mouth there is a sac or cheek pouch, as in some of the ape and monkey tribes, in which they transport the grain that they hoard up in theit subterraneous granaries.

Mus cricetus of Linnæus.

Gen. 4. Dipus of Gmelin.-Pedibus posterioribus multo longioribus. Gerboas. Possess the same sort of teeth as the rats; tail long and tufted at the end; head large and eyes prominent; hinder extremities far exceeding the anterior in the usual proportion: and hence, the fore feet vanishing in comparison of the hind ones, they have gained the name of dipus (two-footed). The fore feet have five toes; in the hind feet the metatarsus of the three middle toes is formed of only one bone, like that which we call the tarsus in birds.

Gerboa. Mus sagitta. M. jaculus.

Gen. 5. Spalar of Güld.-Incisoribus exertis. Mole-rats. They have the grinders like those of the rats, the hamsters, and the gerboas; but their incisors are too large to be covered by the lips; the ends of the lower pair crossing each other; not pointed; each foot has five toes, short, and with five flat thin nails; tail very short or wanting, as are also the external ears; live under ground; eyes of consequence very minute.

Zemni Hepez. Mus typhlus.

Gen. 6. Bathyergus of Iliger.-Crypterus of Fred. Cuvier. Quaternis molaribus singulis locis cum sinu. Mole-rats of the Cape. These animals have the shape, feet, and the truncated incisors of the preceding; but four of the grinders in each situation, and deeply notched at outer edge; the eye though small is visible; the tail is short.

Mus maritimus of Linné. Gray white, nearly as large as a rabbit.

M. Capensis, brown color; a spot about the eye, ear, and upon the crown of the head; tip of the snout white.

Gen. 7. Helamys of Fred. Cuvier.-Pedatis of Iliger. Bipes incisoribus infra hebetibus. This genus is related to the dipus by the large head and eyes, long tail, and the preponderance of the hind part when counterviewed with that before, though the disproportion be less than in the gerboas. In each situation there are four grinders, each composed of two plates; the fore feet have five toes, which are armed with very long pointed nails; hind feet with only four toes, which are very large and almost like hoofs. This disposition in the number of toes is inverse of that which takes place among the rats. Lower incisors truncated, and not sharpened like those of the gerboa and all the other animals enlisted among the rats, the mole-rats excepted.

Gen. 8. Arctomys.-Molaribus horrentibus. Marmot. Have the incisors in the lower jaw sharpened like the majority of animals comprehended in this subdvision; five grinders in each side above and below, all rough, with points; some of the species hence evince a disposition to eat flesh and feed upon sects as well as herbs. These creatures have short legs, a tail of a moderate size and long, covered with hair; head large and flattened. Mus alpinus. M. babac.

Group Sciuri.

Pilis caudæ arrectis. Squirrels. Tail conspicu ous for the vane-like disposition of the hairs. Gen. 1. Sciurus.-Incisoribus infra valde compressis. They have always been regarded as a distinct genus characterised by the compression of their lower incisors, and by the long tail clothed with dishevelled hairs. The thumb is sometimes reduced to a small tubercle; four grinders on each side above and below, tuberculous, with a small anterior grinder in the upper jaw, which easily falls

out.

Sciurus vulgaris.

S. cinereus, chinchilla.

Masked squirrel, S. capistratus of Bosc.
Great Indian squirrel, S. maximus et macruvus.
Babaresque squirrel, S. getulus.
Sevisse squirrel, S. striatus of Linné.
Hudson Bay squirrel, S. Hudsonius.

Gen. 2. Tumias.-Tamias, rapias, a steward who portions out (Teuva) the meat and lays it up in the larder, rautov. Ground-squirrel. Furnished with cheek-pouches; manner of life subterranean.

A mouse-colored species of this genus is very common in California, particularly about Monterey, where it generally selects some elevated or sunny situation for delving its subterraneous abode. It is a sprightly creature, often running in sportful visitation to the burrows of its neighbours; when a stranger approaches their haunts, they, all in obedience to the instinctive desire of self-preser vation, retire precipitately to their holes; but if he continue motionless some time, the heads of the timorous animals will begin to emerge from their lodgments, and in the space of half an hour the whole body will have in this way made its progressive appearance; and, when they seem to have sufficiently ascertained that no harm is nigh them, they renew their sports and occupations as if un