NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 7 



Type: Holotype is Dawson 3101, Nov. 4, 1946, on sheet 50518, 

 including slides 920-922, in HAHF. 



Type locality: Epiphytic on the apical hairs of Galaxaura found 

 in beach drift 5 miles north of Cabo Pulmo, Baja California, Mexico. 



This species is at first suggestive of Erythrotrichia reflexa (Crouan) 

 Thuret, but is unbranched and different in attachment. Except for this 

 different manner of attachment our plants resemble the unbranched 

 Japanese examples of E. reflexa illustrated by Tanaka, 1944, figs. 9-10. 

 The peculiar creeping basal filament of E. ascendens, however, distin- 

 guishes it from this and other terminally tapering species previously 

 described. 



Erythrotrichia biseriata Tanaka 



Tanaka, 1944, p. 86, figs. 8 A-E. 



Thalli epiphytic, filamentous, unbranched, cylindrical, 1-2 mm. long, 

 10-20 /A in diameter, uniseriate below, of cells usually shorter than broad 

 or subquadrate, rarely longer than broad, the lowermost cell elongated, 

 tapering to the base, to 25 /x long, penetrating the host, sometimes with 

 slight lobing at its lower extremity ; filaments more or less biseriate above 

 through cell divisions to produce monosporangia. 



Type: Holotype is no. 1829(c) in the Herbarium of the Biological 

 Laboratory, Imperial Palace, Tokyo, Japan. 



Type locality : Hatidyo Island, Japan. 



Mexican distribution : Faciflc Baja Calif. — D. 9046 on Colpo- 

 menia, D. 9105 on Leathesia, Islas San Benito, Apr.; D. 9534 on Colpo- 

 menia, Punta Abreojos, Apr.; Gulf of Calif. — D. 711, on Colpomenia, 

 Puerto Libertad, Son., Feb.; D. 565, on Eucheuma, Ensenada de San 

 Francisco, Son., Feb. Sinaloa — Small plants epiphytic on Gelidium at 

 Mazatlan (D. 3624, Dec.) appear to belong here, but are sterile and 

 uniseriate. Their penetrating, basal cells are tapered as in this species. 



Erythrotrichia boryana (Mont.) Berth. 



Berthold, 1882, p. 25; Hamel, 1924a, p. 427 (reprint p. 16), Fig. 

 IIIA; Hamel, 1924, fig. II 1 (p. 290; reprint p. 13). Porphyra boryana 

 Montagne, 1846, p. 150, pi. 13, fig. 2. Erythrotrichia porphyroides 

 Gardner, as interpreted by Dawson, 1951. 



Thalli epiphytic, consisting of a primary, monostromatic basal disc 

 which reaches 50 /a in diameter or more before erect filaments are pro- 

 duced; erect filaments arising potentially from each cell of basal disc, 

 unbranched, 1-2 mm. high or more, attenuate at the base, 10-15 /i, in 



