. Animal biology. Zoology; Biology. 190 METAZOAN PHYLA mollusks in that the two valves of the shell are dorsoventral and not lateral and that the internal structure is more wormUke than mollusk- like. They are often called lamp shells because of the resemblance of the shell, when viewed from the side, to an antique lamp. The ventral valve is larger than the dorsal one and at the margin where the two articulate extends beyond the other, forming a beak. The tip of this beak is pierced by an opening, or foramen, through which is passed a fleshy peduncle which permanently attaches the animal to so
. Animal biology. Zoology; Biology. 190 METAZOAN PHYLA mollusks in that the two valves of the shell are dorsoventral and not lateral and that the internal structure is more wormUke than mollusk- like. They are often called lamp shells because of the resemblance of the shell, when viewed from the side, to an antique lamp. The ventral valve is larger than the dorsal one and at the margin where the two articulate extends beyond the other, forming a beak. The tip of this beak is pierced by an opening, or foramen, through which is passed a fleshy peduncle which permanently attaches the animal to some object. f/e lobe Lophophore Dorsal valve Gonad DIgesh've gjarrd •Shmach 'earf-. 'Peduncle iridium onad Veniral valve Mouth Mantle Fig. 100.—Semidiagrammatic longitudinal section of a brachiopod, Magellania lenticularis. {From VanCleave, "Invertebrate Zoology," after Parker and Haswell, by the courtesy of McGraw-Hill Book Company, Inc.) Brachiopods also possess a lophophore (Fig. 100), which consists of two coiled arms bearing many ciliated tentacles. The function of this lophophore, as in the Bryozoa, is to collect food and draw it into the mouth. A true coelom is present. The animal possesses a heart and blood vessels. The brachiopods are all marine and have lived in the seas since very ancient times. In past ages they have been more abundant than at present, but many of them have come down to us practically unchanged. One, Lingula, lives in the seas today and exhibits the same characteristics as it did in the Silurian period, which, according to different estimates, was anywhere from 25,000,000,000 to 300,000,000 years ago (Fig. 312).. 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 Wolcott, Robert Henry, 1868-1934. New York ; London : McGraw-Hill Book Company, Inc.
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