RIVULARIA. 265 



the filament. Colour pale chestnut, inclining to olive." — 

 Carm. 



2. Raphidia viridis Hass. 



Plate LXIV. Figs. 3. 2. 



Char. Frond very mucous^ soft. Filaments small, elongated. 

 Sheath 7iot evident 



yS marginata. — Filaments rather smaller. Sheath evident. 



Hah. Near Manchester : Mr. Sidehotham. Aberdeen : 



Dr. Dickie. '^c^-t^-^ 



This Raj)hidia is very distinct. It was sent me by Mr. 

 Sidebotham of Manchester put up in fluid. The filaments ^^^^ 

 are not one half so large as those of R. angulosa, but much '^^^. a^- 

 longer ; the sheath in it could not be detected. In the variety '■■' '-^^^'^ 

 ^ the sheath was quite apparent, and I at first was induced to ^ JUL 

 resrard it as altogether different : it is safer however to consider 

 it merely as a variety of R. viridis, or as that species in its 

 perfect condition, the sheath in the specimen sent by Mr. 

 Sidebotham, and which had been put up some time in fluid, 

 having probably become decomposed. 



Section iii. Lit HON EM A Hass. 



Char. Fronds indefinite, truly ramose. Bases of the fila- 

 ments not manubriated. Filaments petrified. 



Derivation. From Xidos, a stone, and vr}^jba, a thread. 

 1. LiTHONEMA CALCAREUM Hass. 



Plate LXY. Fig. 2. 



Char. Fronds large, orbicular, convex, afterwards aggregated 

 into a broad spongy crust zoned tvithin, at length petrified. 

 Filaments slender, adherent, and dichotomously branched. 



R. calcarea Sm., E. B. t. 1799. ; Harv. in Hook. Br. Fl. 



p. 392. ; also in Manual, p. 150. 

 Hab. On rocks and stones in streamlets and the borders of 



subalpine lakes. 



