98 A MONOGRAPH OF THE TERTIARY POLTZOA OP VICTORIA. 



radiate arrangement is not so distinct. Part of each is the growing edge, and they 

 are both evidently segments of an orbicular or expanded zoarium, probably 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 way as those of Cribrilina. The large pores in the neighbourhood of 

 the thyrostome and avicularium are depressions or openings between buttress-like 

 outgrowths from the elevated margins of these structures. The avicularium is of 

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

 an equal extent of the width of the zooecium. 



Phylactella, Hincks. 



Thyrostome more or less circular ; peristome usually deficient 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, excej)t below the thyrostome ; thyrostome large, arched above, 

 no denticles on the lower lip, peristome of lower lip and sides thick, and forming a 

 much-projecting entire semicircular collar extending downwards as a raised triangular 

 prolongation. 



M. 



Allied to the European P. labrosa, but differing in the lower lip being very 

 thick, without any denticle, aud forming a perfect semicircle, as well as in the 

 triangular prolongation downwards. 



I have another species from Bairnsdale, but the specimens are too imperfect for 

 satisfactory description. 



Mucronella, Hincks. 



Thyrostome semicircular or subcircular, the peristome of the lower lip elevated 

 into a projecting process or mucro. 



1. M. prcestans, Hincks. PL XIII., fig. 6. 



Mucronella prastans, Hincks, A.M.N.H., Aug., 1882. 



Zoarium encrusting or bilaminate. Zooecia distinct, elongated, projecting 

 slightly above ; surface smooth or slightly fibrillated, a row of deep elongated areola? 

 directed inwards round the margins ; thyrostome subcircular, peristome prolonged in 



