NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 157 



midribbed, the wings rounded or acute, mostly closely fitting, in the 

 more slender parts tending to be asymmetrical by reduction of one of the 

 wings sometimes almost to the midrib; tetrasporangial conceptacles 

 domoid and strongly rostrate, 650-750 /x in diameter; tetrasporangia 

 oblong-fusiform, 160-180 ju, long; sexual plants not seen. 



Type: Holotype is Dawson 8532, Dec. 21, 1949, on sheet 54745 

 including slide 1413, in HAHF. 



Type locality: 2>^ miles north of South Bluff, at —1.7 foot 

 tide level, Isla Guadalupe, Baja California, Mexico. 



Additional material: Dawson 8393, outer reef at extreme 

 south tip of Isla Gualalupe, Dec. 18, 1949. 



The distinguishing features of this species are its sparse, alternate- 

 pinnate, fastigiate branching confined largely to the mid-portions of 

 the erect thalli, and the long, ligulate terminal branches. The tendency 

 to asymmetry of the intergenicula seems characteristic as also the tend- 

 ency to branch from the flattened surfaces of the intergenicula. 



Bossea sagittata Dawson et Silva 

 Plate 8, fig. 1 ; Plate 32, figs. 1-2 



Thallis 8-10 cm. altis; caulibus erectis plerumque percurrentibus, 

 1-3 ordinibus ramorum oppositorum, pinnatorum, interdum dichotomis; 

 intergeniculis cylindricis ad basim, circa 1 mm. diametro, in partibus 

 superioribus obtuse sagittatis, alis subacutis, costa indistincta, crassiori- 

 bus, 2.0-2.5 mm. longis, 1.8-3.0 mm. latis. 



Thalli saxicolous, 8-10 cm. high, consisting of numerous branched 

 erect axes from the basal crustose stratum ; erect axes mostly percurrent, 

 occasionally dichotomous, cylindrical to compressed or flattened in the 

 lower third and little branched except near the base and (or) by single 

 segment pinnae, above flattened and more or less regularly and abundant- 

 ly pinnately, oppositely branched in 1-3 orders, the branching above often 

 from nearly every segment and tending to be corymbose with the second- 

 ary and tertiary pinnae extending all the way to the tips, but sometimes 

 the fronds very irregular in outline from unequal growth of the primary 

 pinnae and the development of few secondary pinnae; intergenicula 

 cylindrical, barrel-shaped at the base (about 1 mm. in diameter), be- 

 coming compressed and flattened above, but usually remaining relatively 

 thick, especially through the axis, blunt-sagittate in shape with narrow, 

 subacute, distally projecting wings and indistinct midrib, usually about 

 as broad as long, 2.0-2.5 mm. long, 1.8-3.0 mm. broad; genicula uni- 



