. Animal biology. Zoology; Biology. OTHER UNSEGMENTED WORMS 193 223. Phylum Brachiopoda.—The animals included in Brachiopoda (brak i op' o da; G., brachion, arm, and podos, foot) resemble certain mollusks in that they possess a bivalve calcareous shell (Fig. 106). For that reason they have in the past been generally considered as belonging to the field of conchology, the science which deals with the mollusks. They have also been frequently grouped with the Bryozoa in a phylum called Molluscoidea. The brachiopods, however, differ from the bivalve mollusks in that the two valves of the shell are
. Animal biology. Zoology; Biology. OTHER UNSEGMENTED WORMS 193 223. Phylum Brachiopoda.—The animals included in Brachiopoda (brak i op' o da; G., brachion, arm, and podos, foot) resemble certain mollusks in that they possess a bivalve calcareous shell (Fig. 106). For that reason they have in the past been generally considered as belonging to the field of conchology, the science which deals with the mollusks. They have also been frequently grouped with the Bryozoa in a phylum called Molluscoidea. The brachiopods, however, differ from the bivalve mollusks in that the two valves of the shell are dorsoventral and not lateral and that the internal structure is more wormlike 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 / op/70pho/'e' DOfScr/ V(?r/ve Sto/nach MorqinaL sera Pa/Zial Sinuses. Hear-f- Coe/om /Vephr/'cf'um Gof^ac/ va/ve ^oufh Fig. 107.—Semidiagrammatic longitudinal section of a brachiopod, Magellania lenticularis. {From VanCleave, "Invertebrate Zoology," after Parker and Haswell, by the courtesy of the McGraw-Hill Book Company, Inc.) 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. Brachiopods also possess a lophophore (Fig. 107), 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, Ldngula, lives in the seas today and exhibits
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