POLYZOA. 69 



articulata, in which the colonies may be encrusting, or erect and 

 branching, but are without joints. 



The first section includes the Crisiidce. 



Grisia dentkulata (Fig. 19) forms delicate white tufts, in which Case B 2. 

 the flat slender branches are composed of a double row of tubular 



Fiar. 19. 



Crista denticulata. A, natural size ; B, branches magnified. 



cells. The horny joints between the branches are black. The 

 Inarticulata occur as crusts or branching growths. In Tubidipora Case B 2. 

 fiahellaris (Fig. 20) the colonies form little fan-shaped crusts on sea- 

 weeds, Lichenopora Mspida forms little white disks, in which rows 

 of tubular cells radiate from the centre. In Idmonea, the colony is 

 branched, the tubular cells being arranged in parallel rows on each 

 side of the middle line of the branch. 

 The Oyclostomata are all marine. 



