266 RIVULARE^. 



" Fronds one fourth or half an inch in diameter, circular or 

 slightly convex, sometimes greenish, but oftener of a dark 

 chestnut colour. After a time, they run together into a flat 

 spongy crust, of indefinite size. On the smooth face of a 

 rock exposed to the trickling of water, I found a sheet of it 

 upwards of a foot in diameter. When broken the crust ap- 

 pears zoned within, so as to indicate the age of the plant, 

 each zone being equal to a year's growth. At this age, it is 

 always more or less stony, from the absorption of calcareous 

 matter." — Carm. 



2. LiTHONEMA CRUSTACEUM HaSS. 



Plate LXV. Fig. 3. 



Char. Crust very thin, widely spreading. Filaments attenuated 

 at the base, fastigiately branched above the middle. 



Rivularia Crustacea Carm. MS. B. Crustacea Harv. in 

 Hook. Br. Fl. p. 393. ; also in Manual, p. 151. 



Hab. On rocks exposed to the spray of cascades, in the 

 hill streams at Appin : Captain Carmichael. 



" Crust of no determinate extent, extremely thin and slimy, 

 black. Filaments one fourth of a line in length, attenuated 

 at the base, fastigiately branched above the middle of an 

 olive green colour." — Carm. 



This species, although decidedly congeneric with L. calca- 

 reum, may at once be distinguished from it by the fastigiate 

 division of its filaments. 



" If you detect any mistakes of mine, I rely on your superior know- 

 ledge to excuse them ; for who has ever avoided errors in the wide- 

 extended field of Nature ? Who is furnished with a sufficient stock of 

 observations ? I shall be thankful for your friendly corrections, I have 

 done what I could myself." — Linnceus to Haller. 



