Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/467

Rh CARNIVORA.] MAMMALIA 443 preceded by milk teeth shed a few days after birth ; sometimes (as in fig. 123) a sixth upper molar (occasionally developed on one side and not the other) ; all with similar characters, generally uniradi- cular ; crown moderate, compressed, pointed, with a single principal cusp, and sometimes a cingulum, and more or less developed anterior and posterior accessory cusps. Vertebrae : C 7, D 15, L 5, S 4, C f^^^fff FIG. 123. Skull and DenMtion of Otaria forsteri. From Giay, Proc. Zool. Soc., 1872, p. 660. 9-10. Head rounded. Eyes large. Pinna of ear small, narrow, and pointed. Neck long. Skin of all the feet extended far beyond the nails and ends of the digits, with a deeply-lobed margin. The nails small and often quite rudimentary, especially those of the first and fifth toes of both feet ; the best-developed and most constant are the three midille claws of the hind foot, which are elongated, com pressed, and curved. The Otarise, or Eared Seals, commonly called Sea Bears or SeaLions, are widely distributed, especially in the temperate regions of both hemispheres, though absent from the coasts of the North Atlantic. As might be inferred from their power of walking on all fours, they spend more of their time on shore, and range inland to greater dis tances, than the true Seals, especially at the breeding time, though they are obliged always to return to the water to seek their food. They are gregarious and polygamous, and the males are usually much larger than the females, a circumstance which has given rise to some of the confusion existing in the specific determination of the various members of the genus. Some of the species possess, in addition to the stiff, close, hairy covering common to all the group, an exceed ingly fine, dense, woolly under fur. The skins of these, when dressed and deprived of the longer harsh outer hairs, constitute the &quot;sealskin&quot; of commerce, so much valued for wearing apparel, which is not the product of any of the true Seals. The best-known species are 0. stelleri, the Northern Sea Lion, the largest of the genus, from the North Pacific, about 10 feet in length ; 0. jubata, the Southern Sea Lion, from the Falkland Islands and Patagonia ; 0. californiana, from California, frequently exhibited alive in menageries in Europe ; 0. ursina, the common Sea Hear or Fur Seal of the North Pacific, the skins of which are imported in immense numbers from the Prybiloff Islands ; 0. pusilla, from the Cape of Good Hope ; 0. forsteri and others, from the coasts of Aus tralia and various islands scattered over the southern hemisphere. These have been grouped by some zoologists into many genera, founded upon very trivial modifications of teeth and skull. Family TKICHF.CHHXE. In many characters the single genus comprising this family is intermediate between the Otariidae, and Phocidse, but it has a completely aberrant dentition. It has no external ears, as in the Phocidae ; but when on land the hind feet are turned forwards and used in progression, though less completely than in the Otariidae. The upper canines are developed into immense tusks, which descend a long distance below the lower jaw. All the other teeth, including the lower canines, are much alike, small, simple and one-rooted, the molars with flat crowns, The skull is without post- orbital process, but has an alisphenoid canal. Tricheclms, Linn. ; Odobaznvs, Brisson (which some modern zoologists have revived). Dentition of young : i f, c f, p and m. Many of these teeth are, however, lost early or remain through life in a rudimentary state, concealed by the gums. The teeth which are usually developed functionally are i, c , p f , m ; total 18. Vertebrae : C 7, D 14, L 6, S 4, C 9. Head round. Eyes rather small. Muzzle short and broad, with on each side a group of long, very stiff, bristly whiskers. The remainder of the hair cover ing very short and adpressed. Tail very rudimentary. Fore feet with subequal toes, with five minute flattened nails. Hind feet with subequal toes, the fifth slightly the largest, with cutaneous lobes pro jecting beyond the ends as in Otaria ; first and fifth with minute flattened nails ; second, third, and fourth with large, elongated, sub- compressed pointed nails. The Walrus or Morse (T. rosmarus) is found throughout the circum- polar regions, those of the North Atlantic and North Pacific being considered by some zoologists as distinct species, by others as local varieties. It ia gregarious, but, owing to the destruction by the sealers for the sake of its tusks, oil, and hide, it is far less abundant than formerly. The use of the great tusks (which are developed in both sexes, though in the female they are more slender than in the male) appears to be for scraping and digging among the sand and shingle for the molluscs and crustaceans which form its principal sustenance ; they are also formidable weapons of defence. Family PHOCID.S:. The true Seals are the most completely adapted for aquatic life of all the Pinnipeds. When on land the hind limbs are extended behind them and take no part in progression, which is effected by a series of jumping movements produced by the muscles of the trunk, in some species aided by the fore limbs only. The palms and soles of the feet are hairy. There is no pinna to the ear, and no scrotum, the testes being abdominal. The upper incisors have simple, pointed crowns, and vary in number in the different groups. All have well developed canines and -| teeth of the molar series. In those species of which the milk dentition is known, there are three milk molars, which precede the second, third, and fourth permanent molars ; the dentition is therefore 7? , m, the first premolar having as usual no milk predecessor. The skull has no post-orbital process and no alisphenoid canal. The fur is stiff and adpressed, without woolly under fur. Subfamily Phocinee. Incisors f. All feet with five well- developed claws. The toes on the hind feet subequal, the first and fifth not greatly exceeding the others in length, and with the interdigital membrane not extending beyond the toes. Halichoerus. Dentition: i, c {, p |, tn total 34. Molars with large, simple, conical, recurved, slightly compressed crowns, with sharp anterior and posterior edges, but without accessory cusps, except sometinfes the two hinder ones of the lower jaw. With the exception of the last one or two in the upper jaw and the last in the lower jaw they are all uniradicular. Vertebrae : C 7, D15, L5, S4, C14. One species, H. grypus, the Grey Seal of the coasts of Scandinavia and the British Isles. Plioca. Dental formula as the last. Teeth smaller and more pointed. Molars with two roots (except the first in each jaw). Crowns with accessory cusps. Vertebrae: C7, D 14-15, L 5, S 4, C 11-1 4. Head round and short. Fore feet short, with five very strong, sub- compressed, slightly curved, rather sharp claws, snbequal in length. On the hind feet the claws much narrower and less curved. The species of this genus are widely distributed throughout the northern hemisphere, and include P. barbata, the Bearded Seal; P. grosnland- ica, the Greenland Seal ; P. vitulina, the Common Seal ; and P. hispida, the Ringed Seal of the North Atlantic ; P. caspim, from the Caspian and Aral Seas; and P. siberica, from Lake Baikal. See SEAL. Subfamily Stenorhyncliinee. Incisors f. Molars two-rooted, except the first. On the hind feet the first and fifth toes greatly exceeding the others in length, with nails rudimentary or absent. Monachus. Dentition: i |, c ^, p f, m total 32. Crowns of molars strong, conical, compressed, hollowed on the inner side, with a strongly-marked lobed cingulum, especially on the inner side, and slightly developed accessory cusps before and behind. The first and last upper and the first lower molar considerably smaller than the others. Vertebra} : C 7, D 15, L 5, S 2, C 11. All the nails of both fore and hind feet very small and rudimentary. One species, M. albivcnter (Pelagius monachus of some authors), the Monk Seal of the Mediterranean and adjacent parts of the Atlantic. The other genera of this section have the same dental formula, but are distinguished by the characters of the molar teeth and the feet. They arc all inhabitants of the shores of the southern hemisphere. Stcnorhynclius (Ogmorhinus, Peters). All the teeth of the molar series with three distinct pointed cusps, deeply separated from each other ; of these the middle or principal cusp is largest and slightly recurved ; the other two (anterior and posterior) are nearly equal in size, and have their apices directed towards the middle one. Skull much elongated. One species, S. leptonyx, the Sea Leopard, widely distributed in the Antarctic and southern temperate seas. Lobodon. Molars with much-compressed elongated crowns, with a principal recurved cusp, rounded and somewhat bulbous at the apex, and with one anterior, and one, two, or three posterior, very distinct accessory cusps. One species, L. carcinophaga. Leptonyx, Molars small, with simple, subcompressed, conical crowns, with a broad cingulum, but no distinct accessory cusps. L. wcddellii. Ommatophoca.Al the teeth very small; those of the molar series with pointed recurved crowns, and small posterior and still less developed anterior accessory cusps. Orbits very large. Nails quite rudimentary on front and absent on hind feet. The skull bears a considerable resemblance to that of the members of the next subfamily, towards which it may form a transition. There is one species, 0. rossii, of which very little is known. Subfamily Cystophorinee. Incisors f. Teeth of molar series