Zoology.-] NATURAL HISTORY OF VICTORIA. {Polyzoa. 



anterior ridges, and the prominence of the cell-mouths, of course, 

 vary much with age. In some specimens numerous, small, sharp- 

 pointed spines project from the edges of the fenestra?. These, 

 however, are usually absent, even in perfect specimens. The 

 ooecia are very large and prominent. They are seldom confined 

 to one branch, but usually extend over several, generally bulging 

 in the direction of the axis of each branch involved. 



The genus Retihornera has been proposed by Kirchenpaur and 

 adopted by Busk for the fenestrate species of Hornera. Such a 

 species as H. robusta (McG.) shows the transition, and I cannot 

 see any sufficient reason for dividing the old genus. 



Explanation of Figures. 



Plate 118. — Fig. 1, specimen, natural size. Fig. 2, portion of the front of a specimen* 

 magnified. Fig. 3, portion of another specimen, more highly magnified, to show the expanded' 

 lacerated outer lip of the peristome of the zooecia. Fig. 4, portion of the back of a specimen, 

 showing two ooecia. Fig. 5, part of a specimen, with small spines on the edges of the 

 fenestra?. 



Plate 118, Figs. 6 to 8. 



HORNERA ROBUSTA (P. McG.). 



Description. — Zoarium composed of one or more thick, flattened stems, from 

 which lateral branches extend on either side, these lateral branches frequently anas- 

 tomosing- with each other and with those from adjacent stems ; zocecia arranged in 

 numerous longitudinal rows, separated by raised ridges ; mouth in the central zooecia 

 slightly exserted, in the lateral and those near the edge the peristome produced and 

 irregularly dentate ; posterior surface of zoarium longitudinally sulcate, the narrow 

 intermediate ridges thickly punctate. Ocecium large, posterior, elongated in the 

 direction of the branch, pitted. 



Reference.— P. H. MacGillivray, Tr. Roy. Soc. Vict., Dec. 1882. 



Port Phillip Heads. 



H. robusta attains a considerable size, a specimen dredged at 

 Port Phillip Heads being two and a half inches by one and three- 

 quarters. Its mode of growth is very characteristic. It originates 

 from a single stem, usually subcylindrical, but sometimes broad or 



[72] 



