60 A MONOGRAPH OF THE TERTIARY POLYZOA OP VICTORIA. 



at the summit of tlu- tliyrostomo, raised anteriorly and -with tlie l)lunt niandil)l(> 

 directed forwards. 



s.r. 



The zoariuni is small and seemini^ly free. Tlie central elevated ])late is 

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

 Corbnlipunt ovnala in llie central plate and stout marginal ril)s, hiil otherwise 

 differs in the structun- ol' the zo(eciuni, and 1 think there can be no (loui)t that its 

 pro])er place is in Cribrilina. 



Corbulipoi'a, luj. 



Zoarium (M-ect. Zocrcia q\iadriserial, facing to the four sides, nuich elongated, 

 calcareous, readily separating longitudinally, anterior part wider, raised, I'ormed by 

 a scries of vertical ribs on each side, turning al)ruptly inwards and unijing lo form 

 a flat plate; posterior j)art of zoceeia narrow, smooth and entire ; thyrostonie with 

 the upi)er lip arched, thickened and smooth. 



1. C. oniala, u.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 oojcium is shallow, cucullate, arching over the 

 tliyrostome. 



S.P. ; M.C. 



This species resembles Cribrilina elevata in having a central elevated plate 

 supported on vertical marginal ribs. It dill'ers from the other Cribrilinidte in 

 having the zocecia mueh elongated and readily separable laterally, although firmly 

 united at the ends, as well as in their s'mooth extension below the part closed by 

 the marginal ribs and ])late. It cannot, I think, be properly incliid(!d in either 

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

 reception. 



Paniily IIiantoi'ORID.t:. 



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

 Zotucia 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 wliich coalesce, leaving large foramina; th(> Xuw^'jf 

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

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

 with nmnerous calcareous or corneous radical tid)es for attachment to the object 

 over which the zoarium throws. 



