. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ADAPTATIONS IN MALLEUS AND ISOGNOMON 389 B. FIGURE 5. M. malleus, A, very irregular shell (from Rabaul) ; the mantle lobes have withdrawn from the first formed distal (prismatic) regions of the valves to form new ones at a somewhat different angle to the "hinge ; The nacreous region of the shell is not affected; B, umbonal region of left valve showing initial form (resembling Pinctada) imme- diately after settlement (After Jackson, 1890). matic regions with very high conchiolin content (Bevelander and Benzer,
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ADAPTATIONS IN MALLEUS AND ISOGNOMON 389 B. FIGURE 5. M. malleus, A, very irregular shell (from Rabaul) ; the mantle lobes have withdrawn from the first formed distal (prismatic) regions of the valves to form new ones at a somewhat different angle to the "hinge ; The nacreous region of the shell is not affected; B, umbonal region of left valve showing initial form (resembling Pinctada) imme- diately after settlement (After Jackson, 1890). matic regions with very high conchiolin content (Bevelander and Benzer, 1948; Bevelander, 1952; Yonge, 1953b). Malleus albus Lam. The shell of this second hammer oyster (Fig. 6A) differs in being yellowish white and much stouter; the prismatic layer is more heavily calcified. There is less repair and the shells are therefore less irregular. They attain much the same size; the largest measured, from Bougainville in the Solomons, was cm. long with a hinge line of 25 cm. Unlike M. malleus, the shell margins are deeply folded, the two valves interlocking very precisely. As originally noted by Lamarck, the adult shell lacks a byssal notch and Kuhnelt (1938), in a description of a pre- served specimen, found neither byssus nor posterior byssal retractor. As shown in Figure 6A, the corresponding muscle scar has disappeared, covered over by subse- quent secretion of nacreous 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 Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983. Woods Hole, Mass. : Marine Biological Laboratory
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
