. Comparative zoology, structural and systematic. For use in schools and colleges. Zoology. 64 COMPARATIVE ZOOLOGY. are the convex edges of horny semicircles, each bordered by a row of nearly a hundred hai-d, sharp teeth. When the mouth, or suck- er, is applied to the skin, a sawino- to the horny ridges, so that the " bite " of the Leech is re- ally a saw-cut. The dentition of the univalve Mol-. Fio. 27.—Teeth and Masticatory Apparatus of Gastero- pods : A, jiortioD of odontophore, or " tongue," of Vel- utina, enlarged; B, portion of odontophore of Whelk (Duceinnm imdattim)
. Comparative zoology, structural and systematic. For use in schools and colleges. Zoology. 64 COMPARATIVE ZOOLOGY. are the convex edges of horny semicircles, each bordered by a row of nearly a hundred hai-d, sharp teeth. When the mouth, or suck- er, is applied to the skin, a sawino- to the horny ridges, so that the " bite " of the Leech is re- ally a saw-cut. The dentition of the univalve Mol-. Fio. 27.—Teeth and Masticatory Apparatus of Gastero- pods : A, jiortioD of odontophore, or " tongue," of Vel- utina, enlarged; B, portion of odontophore of Whelk (Duceinnm imdattim), magnified —the entire tongue has 100 rows of teeth; C, head and odon tophore of Lim- pet {Patella vtdgata); D, portion of same, greatly mag- nified, to show the transverse rows of siliceous teeth. lusks, or the Snails, is general- ly lingual, i. e., it consists of microscopic teeth, usually si- liceous and amber - colored, planted in rows on the tongue. The teeth are, in fact, the ser- rated edges of minute plates. The number of these plates varies greatly; the garden Slug has 160 rows, with ISO teeth in each row. All Birds, and some other Vertebrates, as Ant - eaters,'" Turtles, Tortoises, Toads, and Sturgeons, have no teetli. Their absence is generally associated with a horny beak, a wide gullet, and a muscular stomach (gizzard). In a few Vertebrates, horny plates take the place of teeth, as the Duck Mole (Ornitho- rliynchus) and Whalebone. 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 Orton, James, 1830-1877. New York, Harper and brothers
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Keywords: ., bookcentury1800, bookdecade1880, bookpublishe, booksubjectzoology
