198 



MOLLUSCA. 



living forms. One of the greatest depots of fossil Polyzoa is 

 the White Crag of Suffolk, which is for this reason very inap- 

 propriately called the " Coralline Crag." Amongst the more 

 important Tertiary genera may be mentioned Eschara, Celle- 

 pora, Flustra, Tubulipora, Idmonea, and Fascicularia (or Mcand- 

 ropora). One of the most singular of these' is the genus Fasci- 

 cularia (fig. 137), in which the coenoecium is more or less 



' ' W 



Fig. 137. Fascicularia (Meandropora) cerebri/ormis, Miocene Tertiary. 



spherical, composed of vertical laminae arranged somewhat 

 like the convolutions of the brain, and carrying the cell-mouths 

 at their extremities. 



CHAPTER XIX. 

 BRACHIOPODA. 



THE Brachiopoda are defined as Molluscous animals in which 

 the body is protected by a bivalve shell > which is lined by expansions 

 of the integument or " mantle." The mouth is furnished with 

 long, spirally-coiled; cirriferous processes or "arms." The animal 

 is never composite. (Fig. 138). 



Fig. 138. Brachiopoda. Teretratula vitrea. i. Showing the ciliated " arms ; " 

 a. Showing the shell with its loop. (After Woodward.) 



The Brachiopoda are essentially very similar in structure to 

 the Polyzoa, from which they are distinguished by the fact that 



