Zoology.'] NATURAL HISTORY OF VICTORIA. [Polyzoa* 



Plate 46, Fig. 1. 



SPIRAL ARIA FLORE A (Busk). 



[Genus SPIRALARIA (Busk). Sub-kingd. Mollusca. Class Polyzoa. Order Infundibu- 

 lata. Sub-Order Cheilostomata. Fam. Flustridae.) 



Gen. Char. — Polyzoary, a narrow and ribbon-shaped lamina spirally twisted round an 

 imaginary axis. Cells in a single layer, opening on the inner surface.] 



Description. — The only species. 



Reference. — Busk, Mic. Journ., vol. i., new ser. ; p. 153. 



Queenscliff and other localities ; not uncommon. 



This beautiful species forms tufts from 1 to 3 or 4 inches high. 

 It consists of a narrow lamina, spirally twisted round an imaginary 

 axis. The branches spring from the margin of the lamina, are 

 from a quarter of an inch to an inch and a half in length, and 

 are usually attenuated at either end. The cells are arranged in a 

 single layer, opening on the inner or upper surface of the lamina. 

 They are irregularly ovoid, generally much narrowed below, sepa- 

 rated by raised margins, along each side of which is a row of 

 minute aculeate spines or denticles. The mouth is shallow, wide, 

 arched above, straight or hollowed below. At one side of the 

 mouth there is a digitiform or club-shaped blunt process. The 

 back of the lamina is marked by narrow raised lines running from 

 the base to the margin, and connected by similar cross ribs. These 

 divide the surface into narrow oblong spaces, having no relation to 

 the true cells, than which they are much smaller. There are two 

 forms of avicularia. All the complete cells at the margin are 

 terminated by sessile avicularia. These are very large, occupying 

 the whole width of the cells, and projecting beyond the free edge 

 of the lamina. The mandibles all open towards the same side. 

 There are other smaller sessile avicularia situated on the front of 

 many of the cells. In some specimens those on the cells approaching 

 the margin are larger, and approximate in structure and size to 

 the large projecting terminal ones. 



Explanation of Figures. 



Plate 46. — Fig. 1, specimen, natural size. Fig. la, a small portion of the inner or upper 

 surface of the lamina magnified. Fig. lb, back of the same, showing the division by narrow 

 raised lines into oblong spaces. 



* In different descriptions " zoarium " is used for " polyzoary," " zooecium " is used for " cell," and " ocecium " is used 



instead of " ovicell." 



[31 ] 



