620 OSCTLLATOEIACEAE. 



crust of a brown color ; the cells are somewhat larger than in the present species, 

 and brownish or yellowish. /;. riulacvu approaches the genus Placoma in the ten- 

 dency of the cells to arrange in radiate filaments, but the tendency is less marked 

 than in Placoma, and the frond is closely adherent to the substratum, not bullate 

 and hollow as in Placoma. 



5. GLOEOTHECE Nag. Gatt. 57. 1S49. 



1. Gloeothece rupestris (Lyngb.) Bornet; Wittr. & Nordst. Alg. Exsice. 399. 

 1880. 

 Palmella rupestris Lyngb. Tent, 207. pi. 69. /. D. 1819. 



On rocks, nearly pure, Caicos Islands : common everywhere in small quantity 

 among other algae, especially in shallow pools, both alongshore and inland ; of gen- 

 eral distribution. Type from Denmark. 



Very variable ; teguments often diffluent, giving the appearance of Aphanothece. 



6. ONCOBYRSA Ag. Flora 10: 629. 1827. 



1. Oncobyrsa marina (Grun.) Eab. Flor. Eur. Alg. 2: 68. 1865. 



Hydrococcus marinus Grun. Verh. Zool.-Bot. Ges. Wien. 11: 420. 1861. 



On Cliondria, Mariguana : Europe ; Africa ; Bermuda. Type from the Medi- 

 terranean. 



Family 2. CHAMAESIPHONACEAE. 



1. HYELLA Born. & Frah. Jour, de Bot. 2: 162. 1888. 



1. Hyella caespitosa Born. & Flab. loc. cit. 



In dead shel's, common : generally distributed. Type from France. 



2. DEKMOCAEPA Crtfuan, Ann. Sci. Nat. Bot. IV. 9: 70. 1858. 



1. Dermocarpa prasina (Eeinscb) Bornet & Thuret : Notes Alg. 75. pi. 26. f. 

 6-9. 1880. 



Spliaenosiphon prasinus Eeinscb, Contrib. 17. pi. 26. f. 1. 1875. 



On Catcnella Opuntia pinnata, Berry Islands ; probably to be found wherever 

 the host occurs : Europe. Type from Europe. 



The common species of the New England coast, which has passed under this 

 name, has much larger cells, and was segregated by Borgesen as D. Farlowii. 



3. XENOCOCCUS Thuret, Ann. Sci. Bot. VI. 1: 373. 1875. 



1. Xenococcus Schousboei Thuret in Born. & Thur. Notes Alg. 76. pi. 26. f. 1-2. 



1880. j> 



Attached to wall of Lyngiya sp., Atwood Cay : of general distribution. Type 

 from northern Africa. 



Family 3. OSCILLATORIACEAE. 



1. OSCILLATORIA Vaucber, ex Gomont, Monogr. 218. 1893. 



Trichomes not torulose, 4-1 0/x in diameter. 4. O. tenuis. 

 Trichomes distinctly torulose. . 



Stratum and trichomes red or red-brown. 2. O. miniata. 

 Stratum and trichomes aeruginous or chalybeous. 



Trichomes 10-20 w in diameter, apex straight. 1. O.sancta. 



Trichomes 6-10 a in diameter, apex usually curved. 3. O. Coralhnae. 



1. Oscillatoria sancta Kiitz. ex Gomont, Monogr. 229. pi. 6. f. 12. 1893 



Atwood Cay : generally distributed, normally in fresh water. Type from Italy. 



2. Oscillatoria miniata Hauck ex Gomont. Monogr. 236. 1893. 



Floating, with Trichodesmium ThiebautU, in Gulf Stream between Gun Cay and 

 Florida : Bermuda ; Guadeloupe ; and Adriatic Sea. Type from Adriatic Sea. 



