98 A MONOGRAPH OF THE TERTIARY POLYZOA OP VICTORIA. 



radiate avrang'eiuont is not so distinct. Part of each is tlic growing edge, and they 

 arc hoth cvid(>ntly segments of an orljicnlar or expanded zoarium, prohably free as 

 in the genera mentioned. The structure of the zooecia, however, is totally different. 

 The pores in the front wall are small, closely and irregularly placed, and not formed 

 in the same Avay as those of Cribrilina. The large pores in the neighhourhood of 

 the thyrostome and aviculnrium are depressions or openings between l)uttress-like 

 outgrowths from the ele\-ated margins of tliese structures. The avicularium is of 

 great size, situated to the side of and a little helow the thyrostome, and occupying 

 an equal extent of the width of the zooecium. 



Phylactella, HiucJcs. 



Thyrostom(» more or less circular ; peristome usually deiicient above, much 

 elevated below and on the sides, not chanelled or sinuated. 



1. P. porosa, n.sp. PL XIII., fig. 2. 



Zoarium encrusting. Zooecia distinct, broad, convex ; surface with numerous 

 small round pores, except below the thyrostome ; thyrostome large, arched above, 

 no denticles on tli(> low(>r lip, peristome of lower lip and sides thick, and forming a 

 much-projecting entin* seinieiicular collar extending downwards as a raised triangular 

 prolongation. 



M. 



Allied to the European P. labrosa, but differing in tlH> lower lip being vei-y 

 thick, without any denticle, and formuig a perfect semicircle, as well as in tlie 

 triangular prolongation downwards, 



I have another species from Bairnsdale, but the sp(>cimens are too imperfect for 

 satisfactory description. 



Mucronella, Iliiwks. 



Thyrostome semicircular or subcircular, the peristome of the lower li]i elevated 

 into a proj(icting process or mucro. 



1. M. 2)rcestans, Hincks. PL XIII., fig. 6. 



Mucronella p7'(Psta)is, Hincks, A.M.N.H., Aug., 1882. 



Zoarium encrusting or bilaminate. Zocccia distinct, elongated, projecting 

 .slightly above ; surface smooth or slightly fibrillated, a row of deep elongated areolte 

 directed in\vards roimd the margins ; thyrostome subcircular, peristome prolonged in 



