27 



the cells of the S. arcjentea never possess the Ifiteral teeth 

 ohserved in the S. cupressina. The prominent tooth on the 

 external e(li:;e of the apertures of the latter is sometimes 

 found in the former; and the lateral teeth wliich are 

 always absent in tlie S. argentea are sometimes deficient 

 in the S. cupressina; and in such a case it would be almost 

 impossible to decide to which S|)ecies, such a specimen 

 belonged. Ellis says the S. cupressina grows in deep water, 

 while the other is confined to shallower water near the 

 shores. My observations are just the reverse of this ; for all 

 the specimens of the S. argentea which I have found on 

 the Cornisli coast have been at fronj eight to ten leagues 

 from land, in about fifty fathonis water. At what depth the 

 S. cupressina grows about St. Ives I do not know, but the 

 water in that neighbourhood, though deep, is, I believe, 

 rather shallower, than of that portion of the English channel 

 from which my specimens of the S. argentea have come. 



THUIARIA. Fleming. 

 Generic Character: Polypidora plant-like, rooted by tubular 

 fibres, erect, dichotomously branched or pinnated ; the 

 cells sessile, biserial, adnata to the raciiis, or iaibedded in 

 the substance of the stem and branches; vesicles scattered; 

 polypes hydraform. 



The most characteristic difference between this and the 

 preceding genus, and by which it may l)e distinguished at 

 once, is that the cells are injbedded or close to the stem, and 

 the aperture not everted. 



BOTTLE-BRUSH CORALLINE. Thmaria Thvia. "Cells 

 ovato-elliptical, rather acute; vesicles pear shaped." — 

 Sibbald. 



Bottle-brush Coralline, Ellis' Coral., p. 10, no, 9, pi. 5, 

 fig. b B. Sertuiaria Thuja, Ellis and Solander's Zoopli., 

 p. 41. Turton's Lin., vol. 4, p. 67t$. Stewart's Elem., vol. 2, 

 p. 442. Lamouroux's Cor, Flex., p. 193. Thuiaria Thuia, 

 Fleming's Brit. An,, p. 545. Johnston's Brit., Zuoph., p. 137, 

 pis. xiv. and xv., figs. 1, and 2. 



Hab. From deep water. Polperro. 



" Stem percurrent, erect, filiform, rigid, zig-zag, knotted, 

 naked underneath, bearing on the upper part a cylirulricai 

 tuft of dichotomous short equal branches, coming olF alter- 

 nately, and so disposed that four complete a whirl." "Ceils 

 close pressed, arranged in two rows, sub-alternate, smooth, 

 tapered from the base to a contracted orifice." Johnston. 

 A single specimen is all that has yet been obtained. 



The young of this species very much resemi)les the next, 

 (Th. Articuiata), but may always be distinguished from it, 



