. A text-book of agricultural zoology. Zoology, Economic. 264 MOLLUSCA. like mass of teeth (fig. 137) which can be drawn in and out, called the radula, and which is used by snails and slugs in devouring the vegetation. The only- group with which we need deal here is that of the Gasteropoda, as they alone are of any agricultural importance. The others, however, may be briefly referred to, as com- pleting the series of the animal kingdom. Lamellibranchiata. — These are all bi- valve headless MoUusca, whose mantle con- sists of two distinct flaps, each of which secretes one of the valves. They re
. A text-book of agricultural zoology. Zoology, Economic. 264 MOLLUSCA. like mass of teeth (fig. 137) which can be drawn in and out, called the radula, and which is used by snails and slugs in devouring the vegetation. The only- group with which we need deal here is that of the Gasteropoda, as they alone are of any agricultural importance. The others, however, may be briefly referred to, as com- pleting the series of the animal kingdom. Lamellibranchiata. — These are all bi- valve headless MoUusca, whose mantle con- sists of two distinct flaps, each of which secretes one of the valves. They respire by gills placed in the cavity formed by the two halves of this mantle. The cavity so formed communicates (in one division) by a siphon with the exterior (Siphonata). Bivalve shells with the line marked on the inside of the shell —the pallial line, indented (fig. 138, c)-—can at once be dis-. FlG. 137.—Two TEANS- VEESE SEEIES OF TEETH FEOM nADUr,A OF LIM- PET. Much enlaj^gad. (Brit. Mus. Guide.). 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 Theobald, Frederick Vincent, 1868-1930. Edinburgh and London, W. Blackwood and sons
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1899
