This section comprises the Lions, Tigers, Cats, Dogs, etc, in which the heel of the foot is raised entirely off the ground, and the animal walks upon the tips of the toes (fig. 424, C).

Fig. 425.   The Greenland Seal (Phoca Graenlandica).

Fig. 425. - The Greenland Seal (Phoca Graenlandica).

Fig. 426.   Dentition of the common Seal (Phoca vitulina).

Fig. 426. - Dentition of the common Seal (Phoca vitulina).

Section I. Pinnigrada or Pinnipedia

This section of the Carnivora comprises the amphibious Seals and Walruses, which differ from the typical Carnivores merely in points connected with their semi-aquatic mode of life. The body in these forms is elongated and somewhat fish-like in shape, covered with a short dense fur or harsh hairs, and terminated behind by a short conical tail. All the four limbs are present, but are very short, and the five toes of each foot are united together by the skin, so that the feet form powerful swimming-paddles. The hind-feet are of large size, and are placed far back, their axis nearly coinciding with that of the body (figs. 424, 425). From this circumstance, and from the fact that the integument often extends between the hind-legs and the sides of the short tail, the hinder end of the body forms an admirable swimming apparatus, similar in its action to the horizontal tail-fin of the Cetacea and Sirenia. The tips of the toes are furnished with claws, but the powers of terrestrial locomotion are very limited. On land, in fact, the typical Seals can only drag themselves along laboriously, chiefly by the contractions of the abdominal muscles. On the other hand, the Eared Seals (Otariadae) can use their hind-limbs freely upon the land. The ears are of small size, and are mostly only indicated by small apertures, which the animal has the power of closing when under water. The bones are light and spongy, and beneath the skin is a layer of fat or blubber. The dentition (fig. 426) varies, but teeth of three kinds are always present, in the young animal at any rate. The canines are always long and pointed, and the molars are generally furnished with sharp cutting-edges. The lower incisors may be reduced to four or to two in number, or may even be wanting (Walrus); and the upper incisors may fall below the normal six. The dental formula of the common Seal (fig. 426) is:

i

3 - 3

1 - 1

; pm

4 - 4

; m

1 - 1

=

34.

2 - 2

1 - 1

4 - 4

1 - 1

The section Pinnigrada includes the three families of the Earless Seals (Phocidae), the Eared Seals (Otariadae), and the Walruses (Tricheridae).

The typical Seals (Phocidae) are distinguished from the Walruses by the presence of incisor teeth in both jaws, and by canines of moderate size; while the absence of ears and the inability to use the hind-limbs on land separate them from the Otariadae. They form a very numerous family, of which species are found in almost every sea out of the limits of the tropics. They abound, however, especially in the seas of the Arctic and Antarctic regions. They live for the most part upon fish, and when awake, spend the greater part of their time in the water, only coming on land to bask and sleep in the sun and to suckle their young. They appear to be universally polygamous. The body is covered with a short fur, interspersed with long bristly hairs; and the lips are furnished with long whiskers, which act as organs of touch. The seals are very largely captured for the sake of their blubber and skins.

The only common British seal is the Phoca vitulina, which occurs not uncommonly on the northern shores of Scotland, and ranges over almost the whole of the shores washed by the North Atlantic and the seas of Greenland. It is yellowish-grey in colour, and measures from three to five feet in length. Other seals attain a much greater length - the Great Seal measuring from eight to ten feet, and the Elephant Seal (Macro-rhinus) of the South Pacific, reaching a length of twenty feet.

The Eared Seals or Sea-lions (Otariadae) differ from the typical Seals in the possession of small conical ears, and in the much greater freedom of the limbs, enabling the animal to walk with comparative ease on land. The Eared Seals are principally found on the shores of the continents and islands washed by the Pacific ; but they are also found in the extreme southern part of the Atlantic as far northwards as the mouth of the Rio Plata.

Fig. 427.   Skull of the Walrus (Trichecus rosmarus), after Owen. i Tusk like upper canines.

Fig. 427. - Skull of the Walrus (Trichecus rosmarus), after Owen. i Tusk-like upper canines.

The third family of the Pinnigrade Carnivores is that of the Triche-cidae, comprising only the Walrus or Morse (Trichecus rosmarus). The chief peculiarity by which the Walrus is distinguished from the true Seals is found in the dentition. According to Owen, there are six incisors in the upper jaw and four in the lower; but these are only present in the young animal, and soon disappear, with the exception of the outermost pair of upper incisors. The upper canines are enormously developed, growing from persistent pulps, and constituting two large pointed tusks, which attain a length of over fifteen inches (fig. 427). The direction of the tusks is downwards and slightly outwards, and they project considerably below the chin. The upper jaw has three praemolars and two molars, with flattened crowns, on each side, and the lower jaw has the same number of premolars and a single molar on each side ; but the true molars are caducous, so that the dental formula of the adult animal is:

i

1 - 1

; c

1 - 1

; pm

3 - 3

; m

0 - 0

=

18.

0-0

1 - 1

3 - 3

0 - 0

Except as regards its dentition, the Walrus agrees in all essential respects with the Seals. It is a large and heavy animal, attaining a length of from ten to fifteen feet or upwards. The body is covered with short brownish or yellowish hair, and the face bears many long stiff bristles. There are no external ears. The chief use of the tusk-like canines appears to be that of assisting the unwieldy animal to get out of the water upon the ice; but they doubtless serve as weapons of offence and defence as well, and they are used for digging up burrowing shell-fish out of the sand. The Walrus is hunted by whalers, both for its blubber, which yields an excellent oil, and for the ivory of the tusks. It is found, living in herds, in the Arctic seas, being especially abundant at Spitzbergen and Nova Zembla.