. Comparative zoology, structural and systematic. For use in schools and colleges. Zoology. HOW ANIMALS EAT. 63 trituration of solid food. If wanting, the legs are often armed with spines, or pincers, to serve the same purpose, as in the Horse-shoe Crab; or the stomach is hned with "gastric teeth," as in some marine Snails; or the deficiency is supplied by a muscular gizzard, as in Birds, Ant-eaters, Insects, and Cuttle-fishes. Even the Lobster and Ci-ab, in addition to their complicated oral organs, have the stom- ach furnished with a powerful set of teeth. The Sea-urchin is the fir
. Comparative zoology, structural and systematic. For use in schools and colleges. Zoology. HOW ANIMALS EAT. 63 trituration of solid food. If wanting, the legs are often armed with spines, or pincers, to serve the same purpose, as in the Horse-shoe Crab; or the stomach is hned with "gastric teeth," as in some marine Snails; or the deficiency is supplied by a muscular gizzard, as in Birds, Ant-eaters, Insects, and Cuttle-fishes. Even the Lobster and Ci-ab, in addition to their complicated oral organs, have the stom- ach furnished with a powerful set of teeth. The Sea-urchin is the first of animals, and the only one below Articulates and Mollusks, which exhibits any thing like a dental ap- paratus. Five calcareous teeth having the shape of three - sided prisms, each set in a triangular pyr- amid, or " jaw," are moved upon each other by a complex arrange- â ^'*'- 26.âEchinus bisected, showing masticating appai-atns. ment of levers and muscles. Instead of moving up and down, as in Yertebrates, or from right to left, as in Articu- lates, they converge toward the centre, and the food passes between ten grinding surfaces. The minute Eotifers (a group of minute Arti(;nlates) liave a curious pair of horny jaws. That which answers to the lower jaw is fixed, and called the "; The upper jaw consists of two pieces called "hammers," which are sharply notched, and beat upon the "anvil" between them. The horny-toothed mandibles of Insects, already men- tioned, are mainly prehensile, but also serve to divide the food in a measure. The three little white ridij-es in the mouth of the Leech. 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
