NO. 10 DAWSON : MARINE ALGAE, GULF OF CALIFORNIA 333 



collected by Liebmann on the tropical coast of America (probably cen- 

 tral Mexican coast) and has clarified the status of certain California 

 plants which have been referred to this species. 



The writer has re-examined a considerable number of specimens from 

 both California and the Gulf in light of the description of Polysiphonia 

 villum given by J. Agardh and is convinced that they should be identified 

 with Liebmann's Mexican plant. The distribution of this species can be 

 stated as embracing the coast of California, the Gulf of California, the 

 central Mexican coast, and perhaps the Galapagos Archipelago. One 

 specimen from the latter region seems to match some of the other ex- 

 amples very closely. 



D. 291, lower littoral rocks, Puerto Refugio, Jan.; D. 430a, lower 

 littoral. Pond Island, Feb.; D. 113, reef rocks. Turner's Island, Jan.; 

 D. 737, 754, same locality, July. 



Lophosiphonia mexicana sp. nov. 

 Plate 48, Figs. 7-10 



Frondes caespltosae, 2 mm. altae, partibus prostratis per rhizinas copiosas 

 discis adhaerentibus deuntibus formantibus, celluHs pericentralibus plerumque 6, 

 vulgo 55 \i crassae, filis erectis 1-2 mm. longis, attenuatis sed non gracilibus, 70-80 

 H diam., in partibus maximis basim usque ad 60-50 )i attenuatis cellulis in partibus 

 angustioribus pericentralibus 6, usque ad 12 in partibus latioribus divisis. 



Plants caespitose, 2 mm. high, of prostrate rooting filaments giving 

 off erect filaments; prostrate parts forming abundant rhizoids without 

 attachment disks, these arising in groups, one from the middle of each 

 successive pericentral cell in a vertical row and showing conspicuous ab- 

 sence of breaks in the series; prostrate filaments with usually six peri- 

 central cells, about 55 /a thick; erect filaments 1-2 mm. long, attenuated 

 but not slender, 70-80 ^i diam. in most portions, narrowing to 60-50 ju, 

 at base, with 6 pericentral in narrower parts, these dividing to twelve 

 in wider parts; apices with a few hairs; tetrasporangia in a slightly ir- 

 regular row, 5-10 segments long in ends of erect branches. 



Type : D. 430, scraped from lower littoral rocks with other minute 

 algae, Pond Island, at south end of Angel de la Guardia Island, Feb. 4, 

 1940. 



H. 238a, Sulphur Bay, Clarion Island, Revillagigedo Group, March 

 24, 1932. Herb. AHF no. 62. 



The most distinctive character of this species is the broadening of the 

 erect branches in their mid- and upper parts by the division of the peri- 

 central cells to 12 from the original 6. The result is usually a complanate 



