Zoology.] NATURAL HISTORY OF VICTORIA. \JPolyzoa. 



Plate 5?, Fig. 2. 

 BIFLUSTRA DELICATULA (Busk). 



Description. — Cells quadrate, usually not more than twice as long as broad ; 

 margin very thick and regularly granular or tubercular ; lamina thick, granular on 

 the surface and edges, leaving a broadly elliptical aperture. 



Keference. — Busk, Crag Polyzoa, p. 72; pi. i., fig. 1. 



Queenscliff. 



Like the last, B. delicatula usually occurs in two layers, forming 

 a cavernous mass ; and of this condition I have fine specimens 

 from Port Curtis, in Queensland. The cells are broader than in 

 B. fragilis ; the septa and lamina much thicker and more strongly 

 granular ; the markings extending almost as short transverse 

 ridges. The only Victorian specimen I have seen occurs in a 

 Membranipora form as a single layer creeping over a narrow sea- 

 weed. In it the cells are much smaller, but do not otherwise differ 

 from those of the Port Curtis specimens. The serrated denticle at 

 the bottom of the aperture exists only in two or three of the cells 

 of the Queenscliff specimen, and is altogether absent in those from 

 Queensland, but, with that exception, they agree precisely with 

 Busk's description and figure. 



Explanation of Figures. 



Plate 57. — Fig. 2, portion, magnified, of a specimen from Port Curtis, in which the cells 

 were arranged in a double layer, the polyzoary being twisted and cavernous as in fig. 1. Fig. 

 2a, end view of cells from the same specimen, showing the dovetailed arrangement which 

 frequently, but not always, exists in this species. Fig. 3, specimen occurring in a single layer, 

 encrusting a narrow seaweed. Fig. 3a, portion of the same specimen, magnified to the same 

 extent as fig. 2. Fig. 36, a small group of cells from the same, more highly magnified ; the two 

 large cells show the broad serrated denticle at the bottom of the aperture. 



The genus Biflustra was proposed by D'Orbigny for a large 

 number of forms, mostly fossil, characterised by having cells similar 

 to those of Membranipora, but disposed in two layers placed back 

 to back and easily separable. All the species figured in the 



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