612 



BRACHIOPODA. 



The Brachiopoda, which were formerly very numerous, both in genera, 

 species, and individuals, are now represented by a little over a hundred 

 species, distributed among some fifteen or sixteen genera. 



Fig. lO.Spirifer sulcatus. A specimen, natural 

 size, atid an enlargement of the middle part 

 of the hinge-area (A.) of the ventral valve, 

 showing the delthyrium almost closed by 

 two deltidial plates (.)> so that only a small 

 foramen (F.) remains. 



r. 11 Lophophore supports in Mayel- 

 lania(m.)&nd Atrypa(a.). m.s., median 

 septum; c., crura; c.p., crural processes; 

 j.p., jugal processes; d.l., descending 

 'lamella a.l. ascending lamella ; p.l., 

 primary lamella ; s.c., spiral coils. 



The Brachiopoda have often been grouped together with the other forms 

 that have a lophophore (Bryozoa, etc.) under the name Molluscoidea (mol- 

 lusc-like). But, while they certainly are not related to the Mollusca, it is 

 very doubtful how far they are allied to these other forms. It is therefore 

 safer to keep them as a separate group of the animal kingdom. 



