536 ON BEYOZOA FROM ZANZIBAR. 



Plate LXXII. 



Fig. 1. Hetepora monilifera , var. ttmbonata MacG. X 25. Showing in the lower 

 zoojcia the large pore within the oral aperture, and 

 in the vipper zoctcia the stalked disc which grows iii 

 front of this pore. From Victoria. 



X 85. Aperture showing the stalked disc. 



X 50. The disc is shown larger and can now he- 

 recognised as the commencement of the wall of the 

 ovicell. 



X 50. The same rather larger. 



X 50. The sides of the ovicell are commencing to 

 grow, but the ovicell is entirely open in front. 



X 50. The ovicell showing a large cruciform opening. 



X 50. The ovicell shows the complete trifoliate- 

 stigma. 



8. Iietepo7-a denticulata Busk. X 250. Section of the proximal end of the 

 zooecinm showing the muscles (in.) attached to the base of the polj'pide- 

 and to the wall of the zocecium, which has a chitinous thickening where 

 the muscle is attached. Between the two sets of muscles a thick funi- 

 cular cord (_/.) passes through a large rosette-plate. 



9. Hetejjora prochicta Busk. X 25. From Wasin (520). 



10. Do. do. X 50. Ovicell. 



11. WiyncJiosoon profmidum, var. laminatttm nov. Diagrammatic figure of 

 the aperture and ovicell. 



12. Steganoporella magnilabris Busk. X about 50. Showing the tentaculai- 

 parts attached to the side wall of the proximal 

 corner, while the stomach, etc., is in the other corner 

 connected by a long narrow oesophageal tube. 



13. Do. do. X 50. Operculum of B zocecium. 



14. Do. do. X 50. Decalcified distal end of the zocecium as seen, 

 from the front with the polypide seen through the- 

 wall and {so.) sclerites to which the frontal muscles; 

 are attached. 



15. Do. do. X 250. Section of the edge of the operculum. 



16. Do. do. X 85. Section of the distal wall through two rosette- 

 plates. Probably the fleshy parts belong in part to 

 the distal and in part to the proximal wall. 



17. Do. do. X 50. Section cut through an opercvilum showing a 

 membrane {m.) between the main sclerites. 



18. Do. do. X 50. Operculum of A zocecium. 



19. Do. do. X 85. Decalcified distal end seen from inside witk 

 the basal wall removed. The tentacular sheath {t.s.)< 

 is held by four bands (S.) attached to the distal wall, 

 also there are muscles (t.s.m.) from the distal end of 

 the tentacular sheath to the wall (a.) which divides 

 the zocecium. The large retractor muscles (»*.) are- 

 seen attached to a tendon, while below there is a 

 smaller pair of muscles {d.) not attached direct to. 

 the operculum, but to the frontal wall quite close 

 to the operculum. 



20. Do. do. X 25. Growing end with the membrane covering the- 

 surface. The end zooecia are as yet quite empty 

 and the operculum of a B zocecium {3.) is growing, 

 but no basal sclerite is yet formed. In the second 

 row the frontal calcareous wall only extends a slight 

 way into the zocecium and here the zocecium is still 

 quite empty. Next the short tube (t.) connecting 

 the two parts of the zocecium grows and the lip 

 commences, but is still some distance from thfr 

 frontal membrane, though later it rises right up to- 

 the proximal edge of the operculum. The frontal 

 sclerite {sc.) to which the opesial muscle is attached 

 does not occur in the younger zooecia, but is seen iiij 

 the mature zocjecia. 



