or Little Knotvn, Polyzoa. 117 



and arranged and articulated in the same manner. The 

 figure of M. ciliata in The Decades is badly drawn, the artist 

 having represented the spines as too small and rigid, in this 

 respect resembling M. spinosa. The illustrations which are 

 now given of the three species will, I hope, render their 

 recognition easy. 



Membranipora serrata, M'G. Fig. 5. 



(Trans. Royal Soc, Victoria, 1869.) 



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 on a separate area at the base of a cell, mandible 

 very long ; ovicell small, projecting into the base of the cell 

 above. 



Encrusting sponge, Schnapper Point and Queenscliff. 



At once distinguished from all other species by the curious 

 marginal processes which bear some resemblance to those found 

 in certain forms of Flustia clenticulata, from which, however, 

 it differs in the absence of the characteristic minute denticles 

 and in the much longer and narrower mandible of the avicu- 

 larium. 



Membranipora armata, M'G. Fig. C. 



(Trans. Royal Soc, Victoria, 1869.) 



Cells quadrate, elongated, separated by narrow raised mar- 

 gins ; surface finely granular ; mouth lofty, arched above, 

 straight or slightly hollowed below, with a large blunt process 

 on each side ; operculum hinged; avicularium situated at the 

 base of a cell, mandible broadly lanceolate, with a membranous 

 margin and directed vertically upwards. 



Queenscliff, on algge. 



This species is closely allied to M. mamillar is, from which 

 it differs in the form of the avicularium. In M. mamillaris 

 the stirrup-shaped support of the mandible is situated close 

 to the edge and prolonged into a narrow point upwards, while 

 in M. armata it is broader, shorter, and situated at some 

 distance from the margin. M. armata, moreover, is white, 

 while M. mamillaris is brown or purple.* 



* In my original description of M. mamillaris, the avicularium is described 

 as oblique, from an abnormal specimen, instead of erect. Lamouroux's 

 description of the same species as Flustra mamillaris was overlooked ; a 

 matter, however, of little consequence, as the prominent mamillary pro- 

 cesses suggested the same specific name. 



