35 



Hab. On shells, and on the back of the Corwich crab, 

 common. Polperro. 



This delicate species is commonly found about from one to 

 two and half inches high, " but sometimes attains the height 

 of four inches." It is of a delicate straw colour throughout, 

 but the pinnae are rather lighter than the stalk. The stalk 

 is divided at regular intervals into joints, is smooth an J 

 destitute of cells. The pinnae are alternate and arise in 

 threes from each internode, though 1 have seen specimens in 

 which they arose in piirs. Each pinna arises from an en- 

 largement of the stem, and like the stem, is divided into 

 joints. The joints or internodes are about five or six times 

 as long as their diameter and irregularly waved. The cells 

 are transparent, unilateral, small, distant, cup-shaped and 

 lying on enlargements of the internodes their apertures are 

 patulous and even. Between the cells, one on each internode, 

 is a minute curved denticle, with its convexity turned upwards. 

 The vesicles are sometimes very numerously produced, and 

 are axillary ; when young, ovoid ; but when the gemmules 

 are fit for expulsion, the upper part bursts into deep in- 

 dentations, giving the appearance, as Ellis says, of being 

 "divided like a coronet." 



This species very closely resemble P. setacea in general 

 appearance and shape. of the cells ; but is distinguished from 

 it by having three pinnae on each internode of the stem 

 instead of one; and by having only one denticle between the 

 cells instead of two. 



PLUMULARIA CATHERINA. " SLem plumous, the 

 pinnae opposite, bent inwards ; cells distant, campanulate, 

 with an even margin ; vesicles scattered, pear-shaped, 

 smooth." Johnston. 



Plumularia Catherina, Johnston in Mag. Nat. Hist., vol.6, 

 p. 498, figs. 61, 62. British Zooph., p. 147, vignette no. 8, 

 p. 79, p. 148, fig. 16. 



Hab. On Pinna ingens, in deep water five leagues off* the 

 Deadman; common. 



This is the most slender of all the species I have seen. 

 Its pinnae are opposite, and "instead of being arched bend 

 inwards, so as to render the general form of the coralline 

 concave on a front view, an appearance produced by the 

 pinnae originating not from the sides, but from the anterior 

 face of the stem." Johnston. The cells are minute, cup- 

 shaped, situated on an enlargement of the internodes of the 

 pinnae; and between the cells are numerous minute hollow 

 teeth, visible only under a very high magnifier. The vesi- 

 cles are pear-shaped, with a contracted mouth frequently 



