60 A MONOGRAPH OE THE TERTIARY POLYZOA OF VICTORIA. 



at the summit of the thyrostome, raised anteriorly and with the blunt mandible 

 directed forwards. 



S.P. 



The zoarium is small and seemingly free. The central elevated plate is 

 evidently formed by the fusion and extension of the marginal ribs. It agrees with 

 Corbulipora ornata in the central plate and stout marginal ribs, but otherwise 

 differs in the structure of the zooecium, and I think there can be no doubt that its 

 proper place is in Cribrilina. 



Corbulipora, n.g. 



Zoarium erect. Zooecia quadriserial, facing to the four sides, much elongated, 

 calcareous, readily separating longitudinally, anterior part wider, raised, formed by 

 a series of vertical ribs on each side, turning abruptly inwards and uniting to form 

 a flat plate ; posterior part of zooecia narrow, smooth and entire ; thyrostome with 

 the upper lip arched, thickened and smooth. 



1. C. ornata, n.sp. PI. VIII., figs. 20, 21. 



Characters as for the genus. The number of ribs is 8-10 on each side, and at 

 the angle of each, where it becomes incorporated in the horizontal plate is a small 

 cylindrical protuberance. The ooecium is shallow, cucullate, arching over the 

 thyrostome. 



S.P. ; M.C. 



This species resembles Cribrilina elevata in having a central elevated plate 

 supported on vertical marginal ribs. It differs from the other Cribrilinidse in 

 having the zooecia much elongated and readily separable laterally, although firmly 

 united at the ends, as well as in their smooth extension below the part closed by 

 the marginal ribs and plate. It cannot, I think, be properly included in either 

 Membraniporella or Cribrilina, and I have therefore constituted a new genus for its 

 reception. 



Family Hiantoporid^e. 



Zoarium unilaminate, encrusting or loosely adnate, or erect and bilaminate. 

 Zooecia at first membraniporidan, the front subsequently closed in by a perforated 

 plate formed by the growth from the margins of a series of branching calcareous 

 processes, the extremities of which coalesce, leaving large foramina ; the lower 

 margin of the thyrostome thus formed thickened and entire or raised into a usually 

 aviculiferous mucro. Dorsal surface of zooecia convex in the unilaminate forms, 

 with numerous calcareous or corneous radical tubes for attachment to the object 

 over which the zoarium grows. 



