PLATE XX. 



Fig. 5. Bugula purpurotinda Norman, frontal view. The two lower zcecia 



on the left show the small size of the cecia (a?.) compared with that 



of the embryo {evib.) {av.) avicularium. 



5a. An avicularium which had broken away from its zoecium ; peduncle 



{ped.), mandible [man.), beak {b), muscular apparatus {vuis. app.). 



6. Dorsal view of the same, showing spine {sp.) and avicularium {av.) 

 as seen from the back, and the mode of bifurcation {bifiir.). 



7. Flustra lichenoides sp. nov. Frontal view, showing cecia («?. ) and vari- 

 ation in the number of flattened spines (7?. sp.^. 



ja. A single frond of the same, natural size. 



8. Dorsal surface of the same, showing the radical fibers ( r. f. ) and their 

 mode of attachment to the zcecia. 



9. Membranipora sandalia sp. nov. Upper surface, representing a few 

 zcecia in the second stage. The aperture {ap. ) occupies the distal end 

 of the zoecium. Below it is the uncalcified area («r. ) upon which an 

 avicularium will be formed, and toward which the calcareous thicken- 

 ings converge. 



9fl. One zoecium of the same near the edge of the colony. It is oblong 

 in shape and the aperture («/>.) occupies the whole of the front. 



9^. A zcecium of the same, showing the beginnings of calcification (/. ) 

 and (of.). The future aperture (a/.) is already laid off. 



(338) 



