626 DIATOMEAE. 



5. Calothrix pilosa Harv. ex Born. & Flah. Ann. Sci. Nat. Bot. VII 3- 363 

 1886. 



New Providence : warm waters generally. Type from Florida. 



2. DICHOTHRIX Zan. ex Born. & Flah. Ann. Sci. Nat. Bot. VII. 3 : 



373. 1886. 



Filaments 17-22 # in diameter; branches long, erect. 1. D.fticicola. 



Filaments about 15 # in diameter; branches short, flexuous. 2. D. penicillata. 



1. Dichothrix fucfcola Born. & Flah. Ann. Sci. Nat. Bot. VII. 3: 379. 1886. 



Watling's Island, Castle Island, and Mariguana : Bermuda ; West Indies ; Cen- 

 tral America. Type from Central America. 



2. Dichothrix penicillata Zan. ex Born. & Flah. Ann. Sci. Nat. Bot. VII. 3: 



379. 1886. 



Bimini, Great Bahama, Berry Islands, Castle Island, and Watling's Island : 

 Red Sea ; Florida ; West Indies. Type from Red Sea. 



3. POLYTHRIX Zan. ex Born. & Flah. Ann. Sci. Nat. Bot. VII. 3: 



380. 1886. 



1. Polythrix corymbosa Grunow/ex Born. & Flah. loc. cit. 380. 1886. 



New Providence and Exuma Chain : widely distributed in warm waters. Type 

 from Florida. 



4. RIVTJLARIA Ag. ex Born. & Flah. Ann. Sci. Nat. Bot. VII. 3: 



345. 1886. 



Trichomes tapering from middle to each end. 3. R. polyoUs. 

 Trichomes tapering towards apex only. 



Trichomes 5-9 w in diameter, sheaths wide, loose. 1. R. Biasolettiana. 



Trichomes 2-5 ^ in diameter, sheaths close, compacted. 2. R.nitida. 



1. Rivularia Biasolettiana Menegh. ex Born. & Flah. Ann. Sci. Nat. Bot. VII. 



3: 352. 1886. 



Mariguana and Atwood Cay : Europe ; North America. Type from the Adriatic. 



2. Rivularia nitida Ag. ex Born. & Flah. Ann. Sci. Nat. Bot. VII. 3: 357. 1886. 



New Providence and Exuma Chain : generally distributed. Type from Sweden. 



3. Bivularia polyotis Born. & Flah. Ann. Sci. Nat. Bot. VII. 3 : 360. 1886. 



Watling's Island : Europe ; North America. Type from the Mediterranean. 



Sub-class DIATOMEAE 



Contributed by CHARLES S. BOYER. 



The diatomaceous flora of the Bahamas includes twenty-five or more genera 

 most of which are common to the North American coast. Of this number, 

 however, two genera, Plagiogramma and Mastogloia, are especially prominent. 

 The former is represented by species first described by Greville as occurring 

 on conch shells at Nassau and New Providence. The latter is quite prolific in 

 species on algae collected by Dr. Marshall A. Howe. The forms which, perhaps, 

 are characteristic of the Bahamas are Mastogloia bahamensis Cleve, not very 



