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



Plate 146, Fig. 1. 



CATENICELLA GEMELLA (McG.). 



[Genus CATENICELLA (Blainville). (Sub-kingdom Mollusca. Class Polyzoa. Order 

 Infundibulata. Sub-order Cheilostomata. Family Catenicellidse.) 



Gen. Char. — Branches originating from the summits of each of a geminate pair, or rarely 

 from the sides of ordinary zocecia. Zocecia in single series, but at a bifurcation geminate, or 

 each internode consisting of a geminate pair ; mouth with simple margins, straight or hollowed 

 and entire below, or with a small, rounded notch.] 



Description. — Each internode consisting' of a geminate pair of zocecia, each 

 pair in the main stem giving- origin to two double zocecia, the one pair continuing 

 the stem directly upwards, the other originating a lateral branch, these branches 

 starting alternately right and left; the lateral branches mostly undivided, but 

 occasionally giving off secondary branches ; in the lateral branches, the geminate 

 pairs giving off the next pair alternately from the right and left zocecium ; mouth 

 large, lofty, straight below. Beneath the mouth a series of 5-7 fenestra around an 

 area continuous with that of the mouth, depressed at the margin and slightly 

 bulging centrally ; the mouth and fenestrate area surrounded by a thick margin ; 

 lateral processes large 5 at each upper angle a small, acuminate, chitinous process 

 (possibly the mandible of a small avicularium) ; a minute, marginal, avicularium at 

 the middle of each lateral process on the extremity of a tube-like mark • a small 

 avicularium on a slight elevation between the zocecia. Posterior surface umbonate 

 and finely sulcate. 



Reference. — P. H. MacGillivray, Trans. Roy. Soc. Vict., July 1886. 



Port Phillip Heads, Mr. J. B. Wilson. 



I have only examined two small specimens of this species, which 

 is characterized by the constant gemination and peculiar arrange- 

 ment of the zocecia. The structure of the zocecia is, however, 

 precisely that of the geminate pairs in C. alata, including the 

 anterior avicularia and the chitinous points on the upper angles ; 

 and I at first referred it to that species, an opinion which Mr. 

 Waters has also expressed in a letter to me. I think it ought, in 

 consideration of its peculiar colonial habit, to be ranked as a 

 species, although it is quite possible that the examination of other 

 specimens may show that it is merely a variety of C. alata. 



Explanation of Figure. 

 Plate 146.— Fig. 1, portion of branch magnified, anterior view. 

 Vol. II.— Decade XV.— 2 c. [ 173 



