A MONOGRAPH OP THE TERTIARY POLYZOA OP VICTORIA. 63 



serrated or fimbriated denticle on one side ; thyrostome large, deep, widely arched 

 above, contracted below, the lower edge straight or mostly developing a broad mucro, 

 which may be smooth or serrated on the edge, frequently a small serrated denticle 

 on each side internally, and occasionally one from the npper lip ; zocecium raised 

 round the thyrostome and having a variable number of small, round avicularian 

 pores on small mamilliform or tubular elevations ; small elliptical or rounded 

 avicularia irregularly scattered over the surface of the zoarium ; on the edge of the 

 branches, at the junction of the laminae, a series of large projecting avicularia, with 

 strong down-curved mucro, and the mandible opening downwards. Ooecia very rare, 

 small, deeply immersed. 



S.P. ; M.C.; B. ; C.B. ; C.C. (W.) 



The appearance varies very much, according to the amount of calcification and 

 number and size of the pores. The pores are usually 3-5 in number, of very 

 variable size. In one form, of which I have several specimens, the zoarium is 

 highly calcified, the thyrostome very large and deep, and there are a single, or 

 occasionally two, large pores and numerous small elevated pores, most of which, if 

 not all, are avicularian. I was at first very doubtful of the systematic position of 

 this species, but the examination of specimens in which the growth of the zooecia 

 can be traced shews clearly that it belongs to Hiantopora, as here defined. The first 

 appearance of the zooecium is membraniporidan, with a large elliptical aperture 

 occupying the whole front, except a small portion inferiorly. The margins become 

 thickened, and the aperture is contracted by two calcareous ingrowths on each side, 

 which gradually extend inwards until they meet and coalesce. The upper bar 

 forming the lower lips of the thyrostome is generally the first to be completed ; 

 from these bars other processes are developed to form the pores and the oval mucro. 

 As calcification advances the large pores become contracted or divided, some of the 

 smaller divisions frequently being obliterated. There are rarely fewer than three 

 permanent pores left, although occasionally there is only one of large size ; and 

 generally on one margin, usually the inner or lower, a denticle remains. The 

 mucronate process of the lower edge of the thyrostome is often not median but 

 developed to one side. Small serrated or fimbriated processes or denticles of varying 

 width are also found on its sides, or occasionally on the upper part. Small avicularia 

 are early developed on the margins of the zooecia before calcification is far 

 advanced. 



There is no doubt of its identity with Eschara liversidgei of T. Woods, and I 

 have therefore retained his specific name, although his description is very meagre 

 and unsatisfactory. 



