. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. A B FIGURE 10. T. cancellata with attached organisms. A, shell largely obscured by four individuals of the simple ascidian, Chclyosoma prodnctnin; B, shell carrying two individuals of the ascidian, Pyura haustor, and between these a specimen of the sabellid worm, Endistylia vancouverensis. These snails may be envisaged as moving as high as possible on the irregular surface of the shelly bottom they inhabit, then remaining motionless with mantle cavity open for feeding and respiration. The shell with its dense coating of bris
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. A B FIGURE 10. T. cancellata with attached organisms. A, shell largely obscured by four individuals of the simple ascidian, Chclyosoma prodnctnin; B, shell carrying two individuals of the ascidian, Pyura haustor, and between these a specimen of the sabellid worm, Endistylia vancouverensis. These snails may be envisaged as moving as high as possible on the irregular surface of the shelly bottom they inhabit, then remaining motionless with mantle cavity open for feeding and respiration. The shell with its dense coating of bristles will then present the maximum of well-protected settling surface. Move- ments of the foot appear sufficient to prevent the larger attaching organisms from growing over the shell aperture. Dislodgement by water movements or by the activities of larger animals will provoke renewed upward movement. Because the attaching sponges—tunicates, sabellids and barnacles—are also suspension feeders, the habits of the snail are of major advantage to them. DISCUSSION Two matters remain for final discussion. First there is the significance of T. cancellata as a biological indicator of a certain type of substrate, second the light thrown by consideration of this, and related, species on the probable course of evolution of mesogastropod limpets. The complicated topography of the water passages between the San Juan Islands, together with the great variations in depth and in the local force of tidal 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 Biologic
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
