APPENDIX. 383 



immediately beneath the apex of the posterior lip a small 

 sessile avicularium. OviceUs subglobular, with a scutiform 

 area on the upper surface, marked with several lines on 

 each side, radiating from a central line. 

 Hab. — Bass Strait. 



Parasitic on several zoophytes. This species to the 

 naked eye exactly resembles C. pumicosa, but on closer 

 examination several important differences wiU be observ- 

 able. The cells in C. bilahiata are less rounded and less 

 distinct than in C. pum,ii:osa. As in that species, some of 

 the cells are furnished with an avicularium, and others un- 

 provided with that appendage ; and again, some cells sup- 

 port an ovicell, whilst others do not. The mouth of the 

 unarmed cells in both species is more or less circular and 

 plain, but in C. bilabiata, even in the Tonarmed cells, the 

 mouth is occasionally distinctly bilabiate. In C. pumicosa 

 the avicularium is placed subapically on a soHtary posterior 

 obtuse mucro, but in C bilabiata there are two such pro- 

 cesses longer and more pointed, one in front and the 

 other behind the mouth; the avicularium, as in the former 

 case, being placed immediately below the apex of the pos- 

 terior mucro. The ovicells also differ very much. In 

 C. pumicosa this organ presents several rather large circular 

 spots or perforations ?, whilst in C bilabiata it exhibits a 

 scutiform or horse shoe-shaped area, marked with several 

 transverse hnes on each side of a middle longitudinal line. 



Fam. 7. GEMELLARIAD^. 

 CcUs opposite, in pairs. 



22. DiDYMiA, n. gen. Tab. i. fig. 6. 



Cells joined side by side; opening large, oval; mouth 

 subapical, central. No avicularium. Ovicells contained 

 within a cell, which is central at each bifurcation. 



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