Zoology.-] NATUEAL HISTOKY OF VICTOKIA. \_Polyzoa. 



against the side of the mouth of the contiguous cell. Ooecia globular, smooth, 

 occasionally with the margin thickened. 



References. — Mucronella tricuspis, Hincks, Ann. and Mag. Nat. Hist., Aug. 

 1881 ; M. munita, MacGillivray, Tr. Roy. Soc. Vict., July 1882. 



Port Phillip Heads ; Portland, Mr. Maplestone. 



Of this common species there are two varieties which I, at one 

 time, considered as distinct species. The one, which may be taken 

 as the type, forms, when young, thin glassy layers on Retepores, 

 shells, &c. The oral spines are long and only seen on the marginal 

 zooecia. The whole surface of the zooecia is smooth. In older 

 specimens there is no difference except what is due to increased 

 calcification. The peristome below forms a pouch-like projection, 

 divided superiorly into three parts — a central broader and two 

 lateral sharper projections. The central part is traversed by a 

 shallow, vertical groove which is frequently, as in the figure, 

 replaced by an elevated band or ridge. In the other variety, which 

 I have described as M. munita, the surface of the zocecia is sharply 

 areolated round the margin, and the spines are much thicker and 

 persistent. Even when highly calcified the areolation is frequently 

 retained, although sometimes obliterated. In. one beautifully per- 

 fect young, growing specimen the marginal spines are thick, with 

 conspicuous chitinous articulations ; and many of the zooecia have 

 a calcareous nodule on the front. 



Explanation of Figures. 



Plate 116. — Fig. 2, portion of zoarium of normal form, showing the young marginal 

 zooecia and those fully formed, ooecia, and avicularia projecting on the sides of the mouths of 

 contiguous zooecia. Spines are seen on the marginal zooecia, but not on the others. Fig. 4, 

 small portion of the variety munita, in which, however, the marginal areolation has disappeared. 

 The bases of the persistent spines are shown. 



Plate 116, Fig. 3. 



MUCRONELLA L^VIS (P. McG.). 



Description. — Cells broadly ovate, arranged in linear series, separated by deep 

 grooves, slightly convex, smooth ; mouth rounded above, a broad denticle deep in 

 the lower lip ; peristome raised round the lower lip, produced in the centre into a 

 prominent square or blunt mucro ; six stiff, articulated spines on the upper margin. 

 Ocecium small, globose, smooth, three spines showing on each side in front of it. 



Reference.— P. H. MacGillivray, Tr. Roy. Soc. Vict., July 1882. 



Sorrento, Mr. J. B. Wilson ; Port Phillip Heads, on shells, &c. 



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