Text book of zoology / by J.E.V. Boas ; translated by J.W. Kirkaldy and E.C. Pollard.

Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: Text book of zoology / by J.E.V. Boas ; translated by J.W. Kirkaldy and E.C. Pollard. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    The Pinnipedia are of considerable size, sometimes even gigantic ; they are marine (a few live in large lakes, e.g., the Caspian Sea), moving with the greatest activity by means of the very flexible posterior portion of the body, whilst the large, backwardly-directed, hind feet function as the caudal fin of a fish. They usually come on shore to rest, to breed, etc.; they are littoral forms, but can only move slowly upon land. Eared! Seals and Walruses are able to walk on all four legs; the true Seals hop along with great difficulty, arching their backs and pushing themselves forward by means of the tail endj they rest with the ventral surface on the ground; the fore limbs are not generally used in locomotion. The food consists of Fish and marine Invertebrates (Crustacea, Mollusca). They are usually polygamous; the males are frequently, as in many other polygamous animals, con- siderably larger than the females. They belong principally to cold and temperate regions. 1. Eared Seals (Otariidse). With small pinnae; long neck; fore limbs large; they can walk on the feet which are naked below; there is a large ridge on all fom- feet, lobed on the hind ones; claws in part rudimentary or very small (this holds for all the claws of the foi'e limb, and for the fii'st and fifth of the hind, whilst that of the middle toe of the hind limb is well developed). The males are always much larger than the females. This group comes nearest to the Oai-nivora, and many of the characteristic peculiarities of the Pinnipedia are not well marked. Among these are the so-called Sea- Lions or Sea-Bears, whose skins afford the well-known sealskin.* They inhabit the soutliern watei's of the South Hemisphere, and the northern regions of the Pacific. 2. The Walrus {Tricliechus [Odohienus'] rosmarus) is devoid of pinnas, but in most respects is closely allied to the Otariidse, though very peculiar as regards the dentition. Like the Otariidse this animal can support itself on its fins, which have large borders, the ventral surface of the feet is naked; the structm-e of the claw as in the Otariidse. The young animal has if, c i, m |, but several of the teeth are small and soon fall out or are never cut, so that the adult usually possesses the following functional teeth : i ^, c i, m f. The upper canine is a long tusk, and continues to grow throughout life; the other teeth are conical at first, but later worn right away. The Wah-us feeds on bivalves, worms, etc., which it grabs up with its long tusks from the bottom of the sea. Fairly large; indigenous to the Arctic regions. 3. True Seals {Phocidai). Pinnse wanting: neck short; fore limbs small. The ventral sides of the feet ai'e hairy, and the limbs are absolutely useless for walking; border of the feet nan-ow; claws for the most part well developed. Chiefly in the Arctic regions. (a) The genus Phoca with three iipper, two lower incisors, and compressed, multitubercular molars. The Common Seal (Ph. vUiiUna), occasionally the Riugjed or Marble Seal (Ph. fcetida), and the Greenland Seal (P. (jreenlundica), occur on the shores of Britain. Allied to Phoca is tlie Grey Seal {Halichoarus fjrypus), with conical molars, occurring on the shores of Northern Em-ope, including Britain. * The sealskin of commorce is deprived of the contoui- hairs, so that the woolly fur alone remains; and it has, therefore, a very different appearance from the fresh skin.