Fig. 364. CALOTHRIX SEMIPLENA. 
Colour. Verdigris-green. 
Substance. Rigid. 
Character of Frond. Tufts of very slender, wavy threads {filaments) ; densely interwoven into 
compressed bundles. Filaments unbranched; tubular; containing narrow, cylindrical 
colour-cells ; some of which are apt to run out, leaving empty transparent patches 
in the tubes ; the rest showing through, with division-lines. 
Measurement. One or 2 inches high. 
Fructification. As before. 
Habitat. Our coasts generally. In rock-pools near high-water mark, growing on Corallina 
officinalis and other small alga3. 
Fig. 365. CALOTHRIX HYDNOIDES. 
Colour. Dark olive-green (blackish under the microscope). 
Substance. Rigid ; plush-like, not velvety. 
Character of Frond. Slender, wavy, obtuse threads {filaments) ; some interwoven into a thin, 
flat layer ; others rising up in close, stiff, sharp-pointed tufts ; forming thin patches. 
Filaments not branched, but lying against each other as if they were ; especially 
above, where three or four crowd together, cohering by their ends, and bristling out 
in sharp points ; tubular ; containing narrow, cylindrical black-green colour-cells, 
which show through, with division-lines. 
Measurement. Filaments an inch high. Patches, an inch or two across, on the clayey shore. 
Spreading for several feet on rocks. 
Fructification. As before. 
Habitat. Appin. On the clayey sea-shore near high-water mark. 
Much more rigid and harsh-feeling than C. scopiilorum, and very like pieces of rough plush. 
Known from C. pannosa by much shorter filaments, and the sharp tooth-like tops of the tuft- 
divisions. 
Fig. 366. CALOTHRIX C^SPITULA. 
Colour. Blackish green. 
Substance. Soft ; velvety. 
Character of Frond. Close, very round, cushion-like tufts of densely-packed threads {filaments). 
Filaments upright, wavy, blunt, often twisted into small bundles ; not branched, but 
sometimes lying against each other as if they were ; tubular ; containing very narrow, 
cylindrical colour-cells, which show through ; their division-lines very strongly 
marked. 
Measurement. Tufts from J to 1| inch in diameter. 
Fructification. As before. 
Habitat. Spanish Point at Miltowii Malbay, Co. Clare. In rock -pools near high-water mark. 
Only once found inTreland. 
