POLYZOA. 69 
articulata, in which the colonies may be encrusting, or erect and 
branching, but are without joints. 
The first section includes the Crisiidm. 
Grisia denticulata (Fig. 19) forms delicate white tufts, in which Case B 2. 
the flat slender branches are composed of a double row of tubular 
Fig. 19. 
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Crisialdenticulata. A, natural size ; B, branches magnified. 
cells. The horny joints between the branches are black. The 
Inarticulata occur as crusts or branching growths. In Tubulipora Case B 2. 
flabellaris (Fig. 20) the colonies form little fan-shaped crusts on sea- 
weeds. Lichenopora hispida 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 Cyclostomata are all marine. 
