. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. 134 COMPARATIVE ZOOLOGY. a univalve is frequently closed by a horny or calcareous plate, called " operculum," which the animal carries on its. Fig. 99.—Left Valve of a Bivalve MoMusk (Cytherea Fig. 100.— Section of a Spiral chione): h, hinge ligament; u, umbo; Z, lunule; Univalve (Triton corrugatus): c, cardinal, and t,t\ lateral teeth ; a, a', impres- a, apex; &, spire; c, suture; sions of the anterior and posterior adductor mus- d, posterio
. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. 134 COMPARATIVE ZOOLOGY. a univalve is frequently closed by a horny or calcareous plate, called " operculum," which the animal carries on its. Fig. 99.—Left Valve of a Bivalve MoMusk (Cytherea Fig. 100.— Section of a Spiral chione): h, hinge ligament; u, umbo; Z, lunule; Univalve (Triton corrugatus): c, cardinal, and t,t\ lateral teeth ; a, a', impres- a, apex; &, spire; c, suture; sions of the anterior and posterior adductor mus- d, posterior canal; e. outer cles; p, pallial impression ; s, sinus, occupied by lip of the aperture; /, aute- the retractor of the siphons. rior canal. only by the animal pouring out lime to cement the parts together. They cannot grow together, like a broken bone. Imbedded in the back of the Cuttle-fish is a very light spongy " bone," which, as already observed, is a secretion from the skin, and therefore belongs to the exoskeleton. It has no resemblance to true bone, but is formed, like shells, of a number of calcareous plates. Nevertheless, the Cuttle-fish does exhibit traces of an endoskeleton: these are plates of cartilage, one of which surrounds the brain, and hence may be called a skull. To this cartilage, not to the " cuttle-bone," the muscles are attached. In Vertebrates, the exoskeleton is subordinate to the endoskeleton, and is feebly developed in comparison. It. 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; Birge, E. A. (Edward Asahel), 1851-1950. New York : Harper & Bros.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1883
