OSCILLATORI-A. 257 



ments slender, straight, brittle. Striae suhdistant, scarcely 

 perceptible. 



O. nigra Carmichael, MS, 



This species differs only from tlie following iji the absence 

 of gloss on the filaments ; a diiference which is, in all pro- 

 bability, of specific importance. 



22. OSCILLATORIA TEREBRIFORMIS Ag. 



Plate LXXII, Fig. 4. 



Char. Stratum terrestrial, bluish black, glossy. Filaments 

 slender, straight, brittle. Strije scarcely evident. 

 O. terebriformis Ag. 



Hab. INIarshy places, Aberdeen, JSTov. 1839 : Dr. Dickie. 

 Sussex : Mr. Jenner. Notting Hill : A. H. H. 



A very abundant species. 



23. OSCILLATORIA DECORTICANS Grcv. 



Plate LXXI. Fig. 10. 



Char. " Stratum smooth, glaucous green, membranaceous. 



Filaments very sle?ider, curved, pale bluish green. Striaj 



distant^ — Harv. 

 Grev. Flom Edin. p. 304. C. decorticans Dillw. t. 26. ; 



Ilarv. Manual, 164. 

 /S corticola. — Stratum blackish green. See PI. LXXI. fig. 4. 



O. corticola Carm. MS. 

 Hab. Damp Avails, rotten timber, often on pumps, &c. 



Common. — /3 "on the trunk of an old sycamore where 



the rain water trickled down : " Capt. Carmichael. 



Stratum membranaceous, not very gelatinous, peeling off in 

 large flakes, and imperfectly adhering to paper ; filaments very 

 minute. I strongly suspect that the O. contexta of Carmi- 

 chael is identical with Greville's O. decorticans, the /3 variety 

 is altosjether different. 



