Zoology.-] NATURAL HISTORY OF VICTORIA. \Rolyzoa. 



Form umbonata (P. McG-.). 



Plate 97, Figs. 1-3. 



Description. — Polyzoary foliaceous, expanded, or convoluted; fenestra elliptical, 

 narrower than the interspaces ; cells quadrate or ovate, separated by much raised 

 margins; surface granular, glassy; mouth sloping obliquely backwards ; in young- 

 cells lower lip nearly straight or hollowed, entire, thin; in older with a loop-shaped 

 notch, at one angle of which is an avicularium; this notch frequently bridged over, 

 leaving a small foramen, also sometimes obliterated, in the latter case the lip being 

 thickened, and at its junction with the lateral margins projecting slightly, giving 

 origin to slender, jointed spines; in many of the older cells these spines are very 

 thick and telescopic in appearance, and frequently confined to one side; avicularia 

 very varied, frequently a semilunar one above a fenestra, and also often one with 

 a long, narrow mandible closing in a bidentate rostrum, opening horizontally inwards 

 on the edge of a fenestra ; ovicell prominent, the vertical band ending in the base 

 of a sharp, smooth, umbonate process; posterior surface strongly vibicate, with 

 numerous, small, round avicularia, especially about the edges of the fenestrse. 



Port Phillip Heads, 15 fathoms. 



This form, which is of comparatively small size, is distinguished 

 by the much-raised margins of the cells and the peculiar umbonate 

 process on the ovicell. These characters are usually so marked 

 that it might seem necessary to constitute a distinct species. In 

 some cases, however, the umbonate process scarcely exists, and the 

 vertical band is little more raised than in sinuata. Young cells of 

 munita also frequently have the margins much raised. 



Explanation op Figures. 



Plate 96. — Fig. 1, specimen R. monilifera, normal form, natural size. Fig. 2, young 

 marginal cells, from a similar specimen, magnified. Fig. 2a, other cells from the same specimen. 

 Fig. 2b, older portion, showing ovicells and avicularia. Fig. 3, portion of var. sinuata, showing 

 large sinus, oral avicularia, and spines. Fig. 4, specimen of R. monilifera, form munita, natural 

 size. Fig. 5, young cells of var. lunata. Fig. 5a, another portion of the same specimen, showing 

 a large avicularium. Fig. 56, single cell and avicularium of same specimen. Fig. 6, small portion 

 of another specimen, showing ovicells. Fig. 7, small portion of var. acutirostris, to show large 

 avicularium and structure of the mouth. Fig. 8, small portion of another specimen, showing 

 both semicircular and long-pointed avicularia. 



Plate 97. — Fig. 1, specimen of R. monilifera, form umbonata, natural size. Fig. 2, small 

 portion, magnified. Fig. 2a, ovicell, partly in profile, to show prominence of umbo. Fig. 3, 

 young cells. Fig. 3a, two cells of same specimen, showing the long, jointed spines. 



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