Australian Polyzoa. ]31 



M. mamillaris by the cells being arranged in transverse 

 series instead of being alternate and by the different form 

 of the aviculariuni ; and from the following species by the 

 cells being of uniform size, by the hollow lower lip of the 

 mouth, and by the oral spines, although frequently differing 

 in size, not presenting the same great disproportion. 



M. dispo/r. 



Cells oblong, of two sizes, arranged in concentric series, a 

 row of large cells being followed by two rows of short ; mar- 

 gins raised ; mouth arched above, straight below ; a thick, 

 blunt, hollow spine on each side of the mouth, in the large 

 cells of enormously disproportionate size. 



Portland Bay, on algae— Rev. J. E. T. Woods. 



The characters of this species are so peculiar that it is im- 

 possible to confound it with any other. The cells are of two 

 sorts, the one form about twice the length of the other. 

 One row of long cells is succeeded by a double row of short 

 ones. In the short cells, the oral processes are of nearly 

 equal size, while in the long ones there is on one side of 

 the mouth a small or moderate sized spine, and on the other 

 a large bullate process. 



M. armata. 



Cells elongated, quadrate, separated by raised margins ; 

 aperture entirely rilled in by a thin, granular membrane ; 

 month with a thick hollow process on each side. Avicularia 

 large, usually at the base of a cell, mandible pointed directly 

 upwards. 



On algae, Port Phillip. 



M. serrata. 



Cells quadrate, very much elongated, truncate above and 

 below ; from each side of the margin projecting inwards is 

 a series of short processes expanding and dividing at the 

 ends. Avicularium at the base of a cell, mandible very 

 long. Ovicell small, projecting into the base of the cell 

 above. 



Encrusting a sponge, Snapper Point. 



At once distinguished from all other species by the curious 

 marginal processes, which bear some resemblance to those 

 found in some forms of Flustra denticulate, of which, were 

 it not for the absence of the characteristic minute denticles 

 and the much longer and narrower mandible of the avicu- 

 larium, it might be supposed to be a single layer. 



L 2 



