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vexity of which is turned inwards in the upper and outwards in the under jaw.
Many fossil Artiodactyles, with similar molars, appear to have differed from the Ruminants chiefly by retaining structures which are transitory and embryonic in most existing Ruminants, as, e. g. upper incisors and canines, first premolars, and separate metacarpal and metatarsal bones; these are among the lost links that once connected more intimately the Ruminants with the Hog and Hippopotamus.
The Pachyderms in the Cuvierian system included all the non-ruminant hoofed beasts; they were divided by the great French anatomist into the Proboscidia, Solidungula, and Pachydermata ordinaria, the latter again being subdivided according to the odd or even number of the hoofs. I have on another occasion1 adduced evidence to shew that the right progression of the affinities of the Ungvlata was broken by the interposition of the Horse and other Perissodactyles between the non-ruminant or omnivorous and the ruminant Artiodactyles; and that too high a value had been assigned to the Ruminantia by making them equivalent to all the other Ungulates collectively.
It is interesting, in relation to the needs of mankind, to find that, whilst some groups of Ungvlata, e. g. the Perissodactyles and omnivorous Artiodactyles, have been gradually dying out, other groups, e. g. the Ruminants, have been augmenting in genera and species. Most interesting also is it to observe, that in existing Ungulates there is a more specialized structure, a further departure from the general type, than in their representatives of the miocene and eocene tertiary periods: such later and less typical Mammalia do more effective work by virtue of their adaptively modified structures.
The Ruminants, e. g., more effectually digest and assimilate grass, and form out of it a more nutritive and sapid kind of meat, than did the antecedent more typical and less specialized non-ruminant Herbivora.
1 Proceedings of the Geological Society, November 3, 1847, P- '35"
The monodactyle Horse is a better and swifter beast of draught and burthen than its tridactyle predecessor the miocene Hipparion could have been. The nearer to a Tapir or a Rhinoceros in structure, the further would an equine quadruped be left from the goal in contending with a modern Racer.
With respect to the geographical distribution of the hoofed Mammalia, I may first remark that the order Ruminantia is principally represented by Old World species, of which 162 have been defined; only 24 species have been discovered in the New World, and none in Australia, New Guinea, New Zealand, or the Polynesian Isles.
The Camelopard is now peculiar to Africa; the Musk-deer to Africa and Asia: out of about 50 defined species of Antelope, only one is known in America, and none in the central and southern divisions of the New World. The Bison of North America is distinct from the Bison of Europe. The Musk-ox, peculiar for its limitation to high northern latitudes, is the sole bovine species that roams over the arctic coasts of both Asia and America. The Deer-tribe are more widely distributed. The Camels and Dromedaries of the Old World are represented by the Llamas and Vicugnas of the New. As, in regard to a former (tertiary) zoological period, the fossil Camelidce of Asia are of the genus Camelus, so those of America are of the genus Auchenia. This geographical restriction ruled prior to any evidence of man's existence.
Palaeontology has expanded our knowledge of the range of the Giraffe; during miocene or old pliocene periods, species of Camelopardalis roamed in Asia and Europe. Passing to the non-ruminant Artiodactyles, geology has also taught us that the Hippopotamus was not always confined, as now, to African rivers, but bathed, during pliocene times, in those of Asia and Europe. But no evidence has yet been had that the Giraffe or Hippopotamus were ever other than Old-World forms of Ungulata.
With respect to the Hog-tribe, we find that the true Swine (Sus) of the Old World are represented by Peccaries (Dicotyles) in the New; and geology has recently shewn that tertiary species of Dicotyles existed in North as well as South America. But no true Sus has been found fossil in either division of the New World, nor has any Dicotyles been found fossil in the Old World of the geographer. Phacochcerus (Wart-hogs) is a genus of the Hog-tribe at present peculiar to Africa.
The Rhinoceros is a genus now represented only in Asia and Africa; the species being distinct in the two continents. The islands of Java and of Sumatra have each their peculiar species; that of the latter being two-horned, as all the African Rhinoceroses are. Three or more species of two-horned Rhinoceros formerly inhabited Europe1, one of which we know to have been warmly clad and adapted for a cold climate; but no fossil remains of the genus have been met with save in the Old World of the geographer. One of the earliest forms of European Rhinoceros was devoid of the nasal weapon: it has long been extinct.
Geology has given a wider prospect of the range of the Horse and Elephant, than was open to the student of living species only. The existing Equidce and Elephantidce properly belong, or are limited to, the Old World; ancLthe Elephants to Asia and Africa, the species of the two continents being quite distinct. The horse, as Buffon remarked, carried terror to the eye of the indigenous Americans, viewing the animal for the first time, as it proudly bore their Spanish conqueror. But species of Equus, like species of Mastodon, coexisted with the Megatherium and Megalonyx in both South and North America, and perished with them, apparently before the human period.
The third division of the Gyrencephala enjoy a higher degree of the sense of touch than the Ungulates through the greater number and mobility of the digits and the smaller extent to which they are covered by horny matter. This substance forms a single plate, in the shape of a claw or nail, 1 See my History of British Fossil Mammals, 8vo, p. 350,
which is applied to only one of the surfaces of the extremity of the digit, leaving the other, usually the lower, surface possessed of its tactile faculty; whence the name Unguiculata, applied to this group, which, however, is here more restricted and natural than the group to which Linnaeus extended the term. All the species are 'diphyodont,' and the teeth have a simple investment of enamel.
The first order, Carnivora, includes the beasts of prey, properly so called. With the exception of a few Seals the
incisors are \—- in number; the canines J—J, always longer
than the other teeth, and usually exhibiting a full and perfect development as lethal weapons; the molars graduate from a trenchant to a tuberculate form, in proportion as the diet deviates from one strictly of flesh, to one of a more miscellaneous kind. The clavicle is rudimental or absent; the innermost digit is often rudimental or absent; they have no vesiculse seminales; the teats are abdominal; the placenta is zonular.
The Carnivora are divided, according to modifications of the limbs, into 'pinnigrade,' 'plantigrade,' and 'digitigrade' tribes. In the Pinnigrades (Walrus, Seal-tribe) both fore and hind feet are short, and expanded into broad, webbed paddles for swimming, the hinder ones being fettered by continuation of integument to the tail. In the Plantigrades (Bear-tribe) the whole or nearly the whole of the hind foot forms a sole, and rests on the ground. In the Digitigrades (Cat-tribe, Dog-tribe, &c.) only the toes touch the ground, the heel being much raised.
It has been usual to place the Plantigrades at the head of the Carnivora, apparently because the higher order, Quadrumana, can put the heel to the ground: but the affinities of the Bear, as evidenced by internal structure, e.g. the renal and genital organs, are closer to the Seal-tribe; the broader and flatter pentadactyle foot of the plantigrade is nearer in form to the flipper of the seal than is the digitigrade, retractile-clawed, long and narrow hind foot of the feline quadruped, which is the highest and most typical of the Camivora.
With the exception of the Dingo no true Carnivore exists in Australia, and that wild dog may have as little claim to be considered an autochthon as the low variety of Man, with whom it is sometimes associated in a half-tamed state.
The genus Ursus is represented by species indigenous to Europe, Asia, Africa, and America; but those of the temperate and warmer latitudes of the New World are distinct from the species of the Old World. Certain plantigrade genera, e.g. Procyon (Racoons), Nasua (Coati-mondis) and Cercoleptes (Kinkajous) are peculiarly American: other plantigrade genera, e. g. Mydaus, Ailurus, and Arctictis, are peculiarly Asian.
The genus Hyaena is limited to the Old World, and one species (H. crocuta) to Southern Africa.
The Skunks (Mephitis) are peculiar to America; the viverrine Carnivores to the Old World.
The great fulvous felines (Leo) of Africa and Asia are represented in America by the smaller Pumas: the Old World spotted felines by the Jaguars: the great striped felines (Tigris) are now restricted to Asia.
The principle of the more specialized character of actual organisations receives illustration in the genetic history of the present order.
The genera Felis and Machairodus, with their curtailed and otherwise modified dentition and their strong short jaws, become, thereby, more powerfully and effectively destructive than the eocene Hycenodons and miocene Pterodons, with their numerically typical dentition and their three carnassial teeth on each side of the concomitantly prolonged jaws, could have been.
In the most strictly carnivorous Gyrencephala the paw is perfected as an instrument for retaining and lacerating a struggling prey by the superadded elastic structures for retracting the claws and maintaining them sharp. We next find in