27 



the cells of the S. argentea never possess the lateral teeth 

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

 external edge of the apertures of the latter is sometimes 

 found in the former; and the lateral teeth which are 

 always absent in the S. argentea are sometimes deficient 

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

 impossible to decide to which species, 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 J have found on 

 the Cornish coast have been at from eight to ten leagues 

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

 S. cupressina grows about St. Ives 1 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 niy specimens of the S. argentea have come. 



THUIARI A. Fleming. 

 Generic Character: Polypidom plant-like, rooted by tubular 

 fibres, erect, dichotomously branched or pinnated ; the 

 cells sessile, biserial, adnate to the rachis, or imbedded in 

 the substance of the stem and branches; vesicles scattered; 

 polypes hydraform. 



Tiie most characteristic difference between this and the 

 preceding genus, and by which it may be distinguished at 

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

 the aperture not everted. 



BOTTLE-BRUSH CORALLINE. Tkuiaria Thvia. "Cells 

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

 Sibbald. 



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

 fig. b B. Sertularia Thuja, Ellis and Solander's Zooph,, 

 p. 41. Turton's Lin., vol. 4, p. 678. Stewart's Elem., vol. 2, 

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

 Fleming's Brit. An., p. 545. Johnston's Brit., Zooph., 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 cylindrical 

 tuft of dichotomous short equal branches, coming o(F alter- 

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

 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 resembles the next, 

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



