NO. 10 DAWSON : MARINE ALGAE, GULF OF CALIFORNIA 261 



mature. The late July collections from Turner's Island, too, are depau- 

 perate. Johnston's collections made in June are large and luxuriant, seem- 

 ing to indicate a maximum of development. Undoubtedly, it is of rather 

 wide and general distribution on rocky shores in the upper half of the 

 Gulf being favored by moderately cool water. 



J. 27 (AHF no. 69), San Francisquito Bay, June; J. 12, San Marcos 

 Island, June; D. & R. 3228, tide pools near Guaymas, Dec; D. 105, 

 reef at Turner's Island, Jan., 693, July; D. 492a, Catalina Bay, near 

 Guaymas, Feb.; D. 403, Pond Island, Feb.; D. 387, Tepoca Bay, Feb.; 

 D. 294, Puerto Refugio, Jan. 



Gelidiella acerosa (Forsk.) Feldm.. & Hamel 



Feldmann & Hamel, 1934, p. 6; Okamura, 1936, p. 472, fig. 218. Gelidi- 

 opsis rigida (Vahl) Weber-van Bosse, 1928, p. 427, fig. 172. 

 Echinocaulon rigidum Kiitzing, Tab. Phyc. XVIII, tab. 40, E. 

 spinellum, tab. 39, E. ramulliferum, tab. 39. 

 This is the largest species in our area and is easily recognized by its 

 robust branches, 400-700 jx diam., and wiry texture. It is of more or less 

 tropical distribution in many parts of the world. In the Gulf it has been 

 encountered only in the warmer waters of the southern extremity, pre- 

 ferring protected pools or the shallow waters of quiet lagoons. 



D. 594, growing on or in coral heads on the bottom of shallow San 

 Gabriel Bay, Espiritu Santo Island, Feb.; D. 610, on rocks in oyster- 

 culture ponds, same locality; D. 633, in rock pools, San Jose del Cabo 

 Bay, Feb. 



Gelidiella Hancockii sp. nov. 

 Plate 43, Figs. 1-2 



Frondes usque ad 2 cm. longae, prorsus cylindricae, pro maxima parte 200 |.i 

 diam., e partibus repentibus rhizoideo affixis, multo ramosae; ramis e superficiebus 

 partium repentium pro maxima parte superis, ramis erectis simplicibus, apicibus 

 acutis ; tetrasporangiis in corticibus transformatis ramellorum brevium lente tumi- 

 dorum aut apicium ramellorum positis. 



Plants forming small, tangled tufts on rock surfaces; individual plants 

 to 2 cm. in length, wiry, cylindrical throughout with an average diameter 

 of about 200 ii, much branched from crooked, semicreeping parts which 

 form rhizoidal attachments to rocks or other surfaces by means of abun- 

 dant, short rhizoids which arise in a mass on the under sides ; branching 

 from prostrate parts polystichous but mostly from upper side, the erect 

 branches mostly entire, only occasionally branching secondarily, this being 



