The twelfth order of Mammals is that of the Carnivora, comprising the Ferae, or Beasts of Prey, along with the old order of the Pinnipedia, or Seals and Walruses, these latter being now almost universally regarded as merely a group of the Carnivora modified to lead an aquatic life.
The Carnivora are distinguished by always possessing two sets of teeth, which are simply covered by enamel, and are always of three kinds - incisors, canines, and molars - differing from one another in shape and size. The incisors are generally and are invariably much larger and longer than the incisors. The praemolars and molars are mostly furnished with cutting or trenchant edges ; but they graduate from a cutting to a tuberculate form, as the diet is strictly carnivorous, or becomes more or less miscellaneous.
3 - 3
3 - 3
(except in some seals); the canines are always
1 - 1
1 - l'
Fig. 423. - Permanent dentitition of the Lion (Felis leo). In the upper jaw the letter p3 indicates the upper carnassial, while in the lower jaw the letter m indicates the lower carnassial.
In the typical and most highly specialised Carnivores (such as the Felidae), the last praemolar in the upper jaw, and the first molar in the lower jaw (fig. 423, pm3 and m) are specially developed, and are known as the "carnassial" teeth, having a sharp cutting-edge; whereas in other cases the corresponding teeth are blunt and "tuberculated." Even in their most trenchant condition, the carnassial tooth commonly has a more or less developed tuberculated process or heel, on the inside of its cutting edge. In various Carnivores a number, or all, of the praemolars and molars may be "tuberculate," their crowns being adapted for bruising rather than cutting. As a general rule, the shorter the jaw, and the fewer the premolars and molars, the more carnivorous is the animal. The jaws are so articulated as to admit of vertical but not of horizontal movements ; the zygomatic arches are greatly developed to give room for the powerful muscles of the jaws; and the orbits are not separated from the temporal fossae. The intestine is comparatively short.
In all the Carnivora the clavicles are either altogether wanting, or are quite rudimentary. The toes are provided with sharp curved claws. The teats are abdominal; and the placenta is deciduate and zonular.
The order Carnivora is divided into three very natural sections :
This section comprises the Seals and Walruses, in which the fore and hind limbs are short, and are expanded into broad webbed swimming-paddles (fig. 424, B). The hind-feet are placed very far back, nearly in a line with the axis of the body, and they are more or less tied down to the tail by the integuments.
Fig. 424. - Foot of Carnivora (after Owen). A, Plantigrada, Foot of Bear ; B, Pinnigrada, Hind-feet of Seal; C, Digitigrada, Foot of Lion.
This section comprises the Bears, and their allies, in which the whole, or nearly the whole, of the foot is applied to the ground, so that the animal walks upon the soles of the feet (fig. 424, A).