M A M M A L I A. 



189 



joint. Many of them, however, have tolerably perfect 

 clavicles, and others have imperfect ones, so that 

 they can bring the paw to the mouth without any 

 turning of the elbow ; but as they cannot turn up 

 the sole of the paw, they cannot bring any substance 

 to the mouth except by holding between the two 

 paws sideways. 



In all their organisation, indeed, they are inferior to 

 the three preceding orders ; and the offices which 

 they perform in nature are of a more humble character. 

 Those which subsist on vegetable matter live, habitu- 

 ally in some cases, and seasonally in almost all cases, 

 upon bark and twigs, and even dry sticks ; and it is 

 not a little remarkable that the beaver of the north, 

 notwithstanding all his ingenuity in hut building, 

 should be contented with nearly the same fare as the 

 hippopotamus of the African rivers, which kennels in 

 the foulest ooze that it can find. In proportion as the 

 clavicles are firmer, the animals have more dexterity 

 in their action ; and this admits of a division of them 

 into two sexes, which is rather convenient in the case 

 of animals which are so very numerous, and the greater 

 number of which, from their habits of concealment, 

 are but little known. 



The section with clavicles is by far the more nu- 

 merous of the two, and contains a number of families, 

 some of which, however, do not consist of more than 

 a single genus, or even a single species. The first 

 family, and those which are the most agile animals, 

 are the squirrels, including squirrels properly so called, 

 leaping squirrels with extended parachutes, usually 

 called flying squirrels, the aye-aye, and perhaps a few 

 others. They are almost exclusively tree animals, and 

 exceedingly quick in their motions. The second 

 family consists of the rats, of which there are thirteen 

 or fourteen separate genera, some inhabiting the 

 mountains, some the walls of houses, some the fields, 

 some the margins of the waters, and, in short, almost 

 all sorts of places that can well be imagined. They 

 are the most numerous mammalia on the face 

 of the earth. All of them, however, are ground ani- 

 mals, and some of them inhabit in vast colonies toge- 

 ther. Their numbers show that they are of vast use 

 in wild nature ; and though most of them which fre- 

 quent houses are accounted pests, yet as they multiply 

 very fast in such situations, we must not suppose that 

 even there they are altogether without their use. 

 The jumping hares, the rat moles, the beavers, and 

 various other genera, the species of which are but 

 fuw, and the manners imperfectly known, also belong 

 l<> the selection with clavicles. 



The section without clavicles contains only three 

 families ; but some of them are animals of consider- 

 able interest. One family consists of the porcupine 

 and the allied genera. Another consists of the hares ; 

 and the third of the cavys, including among others the 

 chinchillas of the South American plains, the skins 

 of which are so much esteemed for the beauty of 

 their fur. 



Several of the rodent animals are offensive, on ac- 

 count of their musky smell ; but the flesh of the 

 greater number is eatable, and that of many is highly 

 prized. The skins of many besides the chinchilla are 

 also valuable, on account of their furs, though less so 

 than those of the marten family, inasmuch as the skin 

 and fur are more tender, and the fur is less glossy. 

 The vast numbers in which many of them are ob- 

 tained, and the comparative easiness.of the hunting of 

 them, make some compensation in those respects. 



EDENTATA. As the character from which this 

 small but very singular order of the mammalia gets 

 its name is merely a negative character, the absence 

 of certain parts, and not the possession of them, no 

 conclusion respecting them can be founded upon it, 

 farther than that they are incapable of inflicting an 

 incisive bite with the front part of their mouths. Still 

 they have some characters in common, although those 

 characters differ very much in the several genera 

 which the order comprises. Those characters are the 

 peculiar structure of the claws with which the extre- 

 mities of the toes are armed, and the degree of mo- 

 tion. Generally speaking the claws are large, and in 

 order to fit them for more powerful action, they em- 

 brace the terminal bones of the toes like a sort of very 

 singularly shaped hoofs. This is the character in 

 which they agree ; and those in which they disagree 

 are chiefly the size and form, which vary according to 

 the purposes to which the animals most habitually 

 apply them. There are three of those purposes : 

 holding on upon trees, digging in the ground for the 

 simple purpose of burrowing, or for digging up bulbous 

 roots and earth insects, and also for digging into the 

 bodies of dead animals, into which they enter by 

 making a mine below. The third form is that which 

 is more adapted for tearing open the burrows or col- 

 lections of earth, chips of wood, or other materials of 

 which those insects that live together in numerous 

 colonies construct their habitations. The first and 

 last of these three varieties of claws among those 

 animals, will be found explained, both in their struc- 

 ture and their action, and also illustrated by sketches 

 in the passages already given as explanatory of the 

 feet of sloths and ant-eaters. An example of the 

 third form occurs in the ground hog of Southern 

 Africa, of which a figure will also be found in the 

 course of this article. The whole order are local in 

 their distribution, as well as peculiar in their structure 

 and their habits. Very few of them, and these only 

 of one of the genera, occur in temperate countries, 

 and such as do are confined to America. Cuvier 

 divides them into three families : Tardigrada, contain- 

 ing only the sloths of living animals, and, according 

 to Cuvier's hypothesis, the megatherium, and those 

 other fossil animals which are presumed to have re- 

 sembled it in structure ; Ordinary Edentata, con- 

 taining the armadilloes and a few others, all of which 

 are exceedingly expert at burrowing in the ground ; 

 and Monotremata, comprising the ornithorhynchus 

 and echidna of New Holland, the one of which is a 

 burrowing animal, and the other aquatic in its habits, 

 and seldom coming to the surface excepting in order 

 to breathe. These two are very peculiar animals. 

 There is no question that both of them are mammalia, 

 and there is as little question that they resemble the 

 ordinary edentata in having no teeth, and also in 

 some parts of their internal organisation ; but still 

 their peculiar character, that, of having only one pos- 

 terior opening to the body, is the one in which they 

 differ from all the other known mammalia ; and 

 therefore it seems desirable that they should stand 

 apart and be classified upon it. Enough of their 

 physiology and manners is not yet known for enabling 

 us to fix their place in the system with any thing like 

 precision ; and therefore we shall venture to arrange 

 them as unclassed animals in supplement to the mar- 

 supial ones, because they too require to be classed 

 upon different principles from the mammalia. 



PACHYDERMATA. This is also an order which is 



