. A manual of zoology. Zoology. IV. VERTEBRATA: MAMMALIA, CETACEA. 645 ten molars; Halicore dugong, ludo-Pacific; Rhytina steUeri of the northern Pacific, exterminated in 17G8. Order IX. Cetacea. In external form the whales resemble the sirenians, a result of w\ aquatic life, but the resemblance ends here. The v.'hales are. Fig. 008,—Restoration of skeleton of Ha/(7/ierM/Nt, an extinct sireni:ui. (.\.fti-r ]\Iiss Woodward.) SO that they are commonly inclitded by the laity in that group, and every one speaks of the whale fishery. Head and trunk are scarcely distinguished, the cervica
. A manual of zoology. Zoology. IV. VERTEBRATA: MAMMALIA, CETACEA. 645 ten molars; Halicore dugong, ludo-Pacific; Rhytina steUeri of the northern Pacific, exterminated in 17G8. Order IX. Cetacea. In external form the whales resemble the sirenians, a result of w\ aquatic life, but the resemblance ends here. The v.'hales are. Fig. 008,—Restoration of skeleton of Ha/(7/ierM/Nt, an extinct sireni:ui. (.\.fti-r ]\Iiss Woodward.) SO that they are commonly inclitded by the laity in that group, and every one speaks of the whale fishery. Head and trunk are scarcely distinguished, the cervical vertebrae being very short and more or less com2)letely fused. The hinder limbs are aljsent, and of the pelvic girdle only a small ilium remains, and no sacral vertebrae are developed. The caudal fin is two-lobed and differs from that of a fish in being horizontally flattened; the skin is thick and is sparsely haired or completely naked, in some hair being lacking even in the embryo. Most of the species inhabit the high seas, Inia boliviensis and Platanista gangetica occur in rivers. The fore limbs are modified into flippers, tlie bones of wliicb are of nearly equal size and are jointed only at the shoulder. A dorsal fin ( ' fin backs') occurs in some. The lack of hair is compensated by tlje thick layer of subcutaneous fat (blubber) which, like tlie fat penetrating the spongy bones, tends to lessen the specific gravity. In order that the ani- mals may breathe while feeding, the larynx is prolonged into a tube which extends up through the pharynx to the choanje, from which the nostrils extend directly upwards to the single (Denticetes) or paired (Mys- ticetes) external opening. Since the air driven out with great force con- tains much moisture and tliis is condensed on contact with the cooler external air, the impression was natural that the animals in 'blowing' spouted water. Since the olfactory membrane is degenerate and the olfactory lobes are reduced, the nose is an orga
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1902
