SCHIZOTHRIX — CALOTHRIX. 223 



3. R. applanata., Carra. ; fronds minute, gregarious, orbi- 

 cular, depressed, black ; filaments simple, attenuated, the 

 apices free. Harv. I. c. p. 392. 



On rocks and stones, between tide-marks, Capt. Carmichael. — " Fi'07ids 

 a line in diameter, gregarious, often confluent, circular, depressed, spongy, 

 of an opaque black colour, shrinking, splitting, and becoming grayish in 

 drying. Filaments one-fourth of a line in length, simple, attenuated to a 

 point, loose at the apex, of a bluish green colour." Carm. This seems to 

 differ fi;om R. atra in its depressed form and simple filaments. I am not 

 acquainted with it. 



4. R. ivifida^Ag.; frond large, gelatinoso-coriaceous, lobed 

 and plaited, often bullated, lubricous, shining, deep green ; 

 filaments simple or pseudo-branched. Harv. I. c. p. 393; 

 Wijalt, Alg. Damn. No. 50; Harv. Phyc. Brit. t. Ixviii, 

 Riv. hidlaia, Berk. Gl. Alg. t. 2,/. 1. 



On rocks between tide-marks. Annual. Summer and autumn. South 

 of England and South and West of Ireland. — Fronds tremelloid, tufted or 

 gregarious, much lobed, the lobes sinuous; in a young state compressed 

 and filled with gelatine, in age hollow and distended; from half an inch to 

 an inch in diameter. Colour a deep but very vivid olive-green, lubricous 

 and subgelatinous to the touch. Substance firm, elastic, not easily lace- 

 rated. Filaments either simple or pseudo-branched, waved, laxly set in the 

 interior of the lobe, but closely packed together on the exterior. Stria 

 closely set and conspicuous. 



TI. ScHizoTHRix. Kiitz. [Plate 26, B.] 



"Filaments involved in a thick, lamellar sheath, rigid, 

 curled, thickened at the base, at length longitudinally di- 

 vided. Sperinatia lateral." Kg. Name, from cr^i^w, to divide, 

 and %i|, a hair. 



1. S. Cresswellii, Harv.; forming dense, soft, pulvinate, 

 convex tufts ; filaments very slender, curved, fastigiate, col- 

 lected into branching bundles. Harv. Phyc. Brit. t. clx. 



On sandstone maritime rocks, near high-watermark, exposed to the drip 

 of fresh water. Annual. Winter. Near the Picket rock, Sidmouth, Rev. 

 R. Cresswell. — Spreading over the surface of the rock in continuous, con- 

 vex, roundish or oval patches, which run one into another, and cover the 

 rock fur spaces several inches in diameter. Colour, in the tuft, greenish 

 olive ; in the filaments yellowish. 



III. Calothrix. Ag. [Plate 26, C] 



Filaments destitute of a mucous layer, erect, tufted or 

 fasciculate, fixed at the base, somewhat rigid, without oscil- 



