. Elementary text-book of zoology. S62 CHORD ATA. and the male dugongs have a single pair of tusk-like upper incisors. The place of front teeth is taken by hard horny pads upon the rostrum and mandible. The molar teeth have a pair of transverse ridges, like those of the tapir, and they succeed each other in series, as in the elephant, armadillos and kangaroo. The extant forms are apparently monophyodont. The stomach is fairly complex, with at least two chambers, and the intestine is long. The placental characters are not fully known, but the dugongs have a zonary placenta which is non-deciduat
. Elementary text-book of zoology. S62 CHORD ATA. and the male dugongs have a single pair of tusk-like upper incisors. The place of front teeth is taken by hard horny pads upon the rostrum and mandible. The molar teeth have a pair of transverse ridges, like those of the tapir, and they succeed each other in series, as in the elephant, armadillos and kangaroo. The extant forms are apparently monophyodont. The stomach is fairly complex, with at least two chambers, and the intestine is long. The placental characters are not fully known, but the dugongs have a zonary placenta which is non-deciduate. The mammae are paired and pectoral in position. At the present day the order is limited to a zone between 30° N. and 30° S. of the equator. Fig. 385.—American Manatee {Manatus Americanus) from life. (From Flower and Lyddeker.). Family I.—Manatidffi or Manatees.—Three species found in the rivers felling into the Atlantic basin. They are peculiar in having only six cervical vertebrae. Beneath the homy pads of the jaws are vesti- gial incisor teeth | and the molars may be as many as \{. Family II.—Halicoridae.—The Dugongs are larger and are found in the Red Sea, Indian Ocean and Northern Australia. The males have incisor tusks which are vestigial in the female. The molars do not exceed f. They are more marine than the Manatees. Family III.—Rhytinids.—The Rhytina or Steller's sea-cow was a large sirenian (25 feet) formerly found in the district of Behring Island. It was finally exterminated at the hand of man in 1768. This species had no teeth, their places being supplied by horny pads. Certain fossil forms, such as Halitherium (Miocene), show us that the sirenians were abundant at that epoch and even. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Masterman, Arthur Thomas. Edinburgh, E. &
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