MISCELLANEOUS. 81 



(2.) Cellepora pumicosa. — Plate XXVI. Figs. 7, 8, 9.— The sub- 

 ject of this paragraph has always occurred to me, like the former, as a 

 circular or cylindrical parasitic belt, surrounding other substances. 



The outer surface of larger specimens exhibits various irregularities, as 

 prominences and depressions, apparently corresponding with a similar for- 

 mation of the inner surface. 



Perhaps the thicker parts may consist of more than a single stratum. 



The exterior is composed wholly of cells, with a circular orifice, 

 inhabited by a lively, active, ascidian hydra, having about 14 ciliated 

 tentacula. 



One specimen, which was certainly very old, invested the tube of an 

 Amphitrite ventilabrum, forming a hollow cylinder, two inches and a half 

 in length, by an inch of internal diameter. The interior was very ir- 

 regular ; probably resulting from the presence of other substances on the 

 surface of the tube invested. Both ends were thin, their increment being 

 obviously advancing. — Plate XXVI. Fig. 7. 



Another smaller specimen, with several obtuse prominences, is repre- 

 sented, fig. 8 ; and a portion of the surface, enlarged, with the hydra\ 



fig. 9. 



On a third, a younger and augmenting specimen, an imperfect cy- 

 linder, with attenuated edges, pale grey ova, as I concluded them, were 

 dispersed. 



The colour of this product is generally dingy white, or yellowish. 



Its largest dimensions seem to be attained in deep water. 



The life of most hydrse is short ; but those of fig. 8 apparently sur- 

 vived some months. Such facts are nevertheless difficult to be proved, 

 for we cannot ascertain whether the old or the young are before us. 



Plate XXVI. Fig. 7. Cellepora pumicosa. 



8. Another specimen. 



9. Surface of fig. 8, with hydrse, enlarged. 



(3.) Cellepora ramulosa. — Plate XXVI. Figs. 10, 11, 12, 13. — 



The preceding species are generally very superficial, investing Cellepores, 

 but the present zoophyte approaches more nearly than any other native 



VOL. II. l 



