8 Proceedings of the Royal Society of Victoria. 



The fertile zooecia are obscurely hexagonal with much elevated 

 very rugose and irregularly nodulated margins, forming a 

 pallisade round the central area which is depressed and smooth ; 

 thyrostome the same as in the infertile zooecia ; an avicularium 

 on one or both sides of the thyrostome with a triangular 

 mandible ; ooecia reniform, densely punctate. Below the lowest 

 zooecium in the internode figured there is a large spatulate avicu- 

 larium with the mandible placed horizontally, below which the 

 zoarium is attenuated downwards. Similar avicularia occur 

 occasionally on zoaria bearing infertile zooecia in the same 

 position, and also on other parts of the zoarium, causing then a 

 slight in-egularity in the disposition of the zooecia. 



Localities. — Mornington (T. S. Hall) ; Mitchell River (J. 

 Dennant). 



The portion of the fertile zoarium figured is part of a solitary 

 specimen from Mornington, and is that from which I determined 

 the genus and species ; but after having done so I obtained a 

 large number of specimens from the Mitchell River deposit, most 

 of which were composed of infertile zooecia, a few had fertile, and 

 one or two both fertile and infertile zooecia. The specimen from 

 Mornington is the only one which shows the ooecia perfect ; in 

 those from the Mitchell River only the base or dorsal wall is 

 preserved, the front wall having been broketi or worn off. The 

 perfect internode in all cases is about 0-15 of an inch long, but 

 the fertile and infertile ones differ in the width, the former being 

 0-027 of an inch in diameter, the latter 0*020. 



This is a very interesting and instructive form as it shows the 

 very great and very remarkable difference that may occur 

 between the fertile and infertile zooecia of the same species 

 especially when one specimen bears an ooecium on every zooecium, 

 and another has none ; indeed, had I not found some specimens 

 with both fertile and infertile zooecia I would have considered 

 them to be different species, for in the fertile zooecia, as stated 

 above, the front is depressed and smooth with a very much 

 raised rugose border or margin, like a fence or pallisade, while 

 in the infertile zooecia the front is very convex and covered with 

 mamillae. The only features in common being the thyrostome, 

 the avicularia hj the side of it, the large spatulate avicularia and 

 the zoarial structure. 



