NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 111 



Gruoriella magdalenae sp. nov. 

 Plate 7, fig. 5 



Thallo exigue calcificato, 2 cm. vel plus lato, laxe affixo, intacto 

 arescente, 150-200 /x. crasso, superficie caelamen minutum exhibente; 

 nematheciis tetrasporangialibus baud elevatis, superficiei vegetativae plus 

 minusve aequalibus, plerumque 50 fi vel minus altis; paraphysibus 

 paulum distinctis; tetrasporangiis ovatis, 40-45 /a longis, 19-21 fi latis. 



Thalli forming expanded, deep dull red, very ligbtly calcified crusts 

 to 7 cm. wide on rocks, rather loosely attached by a hyaline ventral 

 film and by a few short, thick rhizoids, drying without splitting, the 

 surface of dry specimens provided with scattered, small, sharp elevations 

 resembling desert hills and ridges, mostly 150-200 ju. thick; hypothallus 

 (as seen from below) of very conspicuous converging, diverging and 

 anastomosing, narrow, fan-shaped groups of cells, these groups accen- 

 tuated by some of the forking cell rows having differentiated contents 

 causing them to appear like veins, the cells 21-29 fj. long, 9-14 /a wide, 

 20-29 fi high, giving rise to ascending, once- or twice-branched, compact 

 cell rows making up the perithallus, the upper cells of these filaments 

 more or less quadrate, 6.0-7.5 /x wide; tetrasporic nemathecia nearly 

 flush with the surface of the vegetative thallus, or at least not promi- 

 nently elevated, usually not exceeding 50 /a deep, 700 /a wide or more, 

 the paraphyses short, rather coarse, not much differentiated from the 

 sterile bearing filaments except for more elongated cells; tetrasporangia 

 ovate, 37-45 /a long, 19-23 /a wide; sexual reproduction not observed. 



Type: Holotype is Dawson 9363c May 4, 1950, in box 55471, 

 including slides 1601-1603, in HAHF. 



Type locality: Growing over Hildenbrandia on a siliceous rock, 

 intertidal, Punta Hughes, Isla Magdalena, Baja California, Mexico. 



Additional material: D. 10413, Punta San Eugenio, Baja 

 Calif., Nov. 1, 1951. 



This species differs from Cruoriella dubyi and from all other des- 

 cribed species, including the several East Indian ones of Weber van 

 Bosse, by its thin, simple, spreading, deep red vegetative thallus, by its 

 shallow, non-elevated nemathecia, short, coarse paraphyses and small 

 tetrasporangia. 



Gruoriella dubyi (Crouan & Crouan) Schmitz 

 Plate 7, figs. 2-3 



Schmitz, 1889, p. 20, Rosenvinge, 1917, p. 193, figs. 115-117; 

 Taylor, 1945, p. 169, in part. Peyssonelia dubyi Crouan & Crouan, 

 1844, p. 367, pi. 11, figs. 6-10; Weber van Bosse, 1916, p. 136. 



