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 Meand- 

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

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



Fig. 137. Fascicularia (Meandropora) cerebriformis, 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. Terebratula vitrea. i. Showing the ciliated " arms ; " 

 2. 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 



