GENERAL ZOOLOGY 







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Fig. 12.13. Portion of a colony of the fresh-water ectoproct Lophopiis cryslallinus. Note the 

 horseshoe-shaped lophophore of the expanded individual, the U-shaped digestive tract, and the 

 opening of the anus outside the ciliated tentacle crown. The individual at the right is 

 retracted; at the left is a recently formed bud. (Reproduced from the engraving by Lyonet 

 in Abraham Trembley, Hisloire de Polypes, Leyden, 1744. This work contains the original 

 description of the species and is accurate in all details. For other contributions of 

 Trembley, see Figure 10.5.) 



ventrally, and in clams they are lateral. Furthermore, the enclosed body of 

 the brachiopod bears no resemblance to that of a mollusk. 



Brachiopods are usually divided into two classes. In the more primitive 

 of these, represented by species of the genus Lingula (Fig. 12.14), the valves 

 of the shell are delicate and chitinous and are not directly hinged upon one 

 another. There is a long, fleshy stalk, occupied by an extension of the 

 coelom; an anus is present; and the lophophore is without any calcareous 

 support. Members of the other class, represented by Terebratulina (Fig. 

 12.14), possess heavier, limy shells which are hinged together; the stalk is 



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