NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 119 



Jania longiarthra sp. nov. 

 Plate 9, fig. 4; Plate 27, fig. 4 



Thallis ad 2.3 cm. altis, dense dichotome ramificatis, valde acutan- 

 gulis, partim irregularfter decussatis; intergeniculis ubique cylindricus, 

 teretibus, baud constrictis, infra 120-150 fx diametro, supra expandenti- 

 bus ad 200 fi, 6-12 diametris longis. 



Thalli to 2.3 cm. high, densely branched, forming a coarse tuft 

 among various low turf-forming algae; branching dichotomous, some- 

 times, or in part, rather prominently but irregularly decussate, erect and 

 with very narrow angles above; intergenicula cylindrical throughout, 

 smooth, unconstricted, 120-150 /x in diameter below, expanding to 200 

 (210) /x, above, 6-12 diameters long; apices subulate; conceptacles not 

 seen. 



Type: Holotype is Dawson 7041, Mar. 14, 1949, in box 55048 

 in HAHF. 



Type locality: Among various turf-forming algae including 

 Jania capillacea, in inner Bahia San Gabriel, Isla Espiritu Santo, Baja 

 California, Mexico. 



Additional material: D. 75a-40, Bahia de Guaymas, Sonora, 

 Mexico, Jan. 23, 1940. 



A rather poorly developed plant, possibly referable here, but with 

 habit modified by Choreonema parasitism, was found 11 miles west of 

 Punta Malarrimo, Bahia Vizcaino, D. 10095, April. It differs from the 

 Gulf material in being slightly attenuated above and in having somewhat 

 larger and considerably shorter intergenicula in lower parts. 



This species is distinguished from others of our coast by its narrow 

 angle of branching and by its very long intergenicula. It appears to be 

 rather rare and confined to protected bays subject to high insolation. It 

 approaches Jania nipponica (Yendo) Yendo in size and habit, but differs 

 by its intergenicula which are longer, cylindrical throughout, and larger 

 in diameter above than below. 



Jania mexicana Taylor 



Taylor, 1945, p. 197, pi. 60. 



Thalli commonly attached to barnacles, or saxicolous, densely tufted, 

 1.5-2.3 cm. high, the branching erect and dense, subcorymbose ; axes 

 cylindrical throughout; segments 340-425 fx long, 170-205 /i in diameter 

 below, 120-150 /a in ultimate segments above; apices obtuse-conical; 

 tetrasporangial conceptacles ovoid, about 300 /t in diameter, antennifer- 



