. Elementary text-book of zoology [electronic resource]. Zoology. 550 CHORD AT A. In Sirefiia there is the same tendency to disappearance of the front teeth as we have noticed in the Edentata and Effodiefitia. The manatees have no functional incisors nor canines 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 rostium and mandible. The molar teeth are a pair of transverse ridges, like those of the tapir Fig- 337-—American Manatee {Manattis americanus) from life. (From Flower and Lyddekek.). and they succeed each
. Elementary text-book of zoology [electronic resource]. Zoology. 550 CHORD AT A. In Sirefiia there is the same tendency to disappearance of the front teeth as we have noticed in the Edentata and Effodiefitia. The manatees have no functional incisors nor canines 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 rostium and mandible. The molar teeth are a pair of transverse ridges, like those of the tapir Fig- 337-—American Manatee {Manattis americanus) from life. (From Flower and Lyddekek.). 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. Family —Manatidae or Manatees.—Three species found in the rivers falling into the Atlantic basin. They are peculiar in havin?^ only six cervical vertebrae. Beneath the horny pads of the ja\A S 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.—Rhytinidae.—The Rhytina or Steller's sea-cow- was a large sirenian (25 feet) inhabiting the district of Behring 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; Parsons, John Herbert, Sir, 1868-1957, donor; S.
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