18 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



Most of these specimens are relatively thin, under 60 ju., and in a 

 few a moderate degree of antheridial segregation has been observed as 

 described by Setchell and Hus for forma segregate. In some of the Islas 

 San Benito and Bahia Asuncion specimens the last division of the car- 

 posporangium is oblique and often irregular. These examples are inter- 

 mediate between the usual carposporangial development in the species 

 and that observed in the Punta Santa Rosalia and Isla Magdalena speci- 

 mens in which the carposporangia regularly divide twice parallel to the 

 thallus surface so that the 32 carpospores are arranged in four tiers in- 

 stead of two. 



Porphyra thuretii Setchell and Dawson 



Setchell and Dawson, apud. Dawson, 1944, p. 253; Smith, 1944, p. 

 171, pi. 40, fig. 2. Porphyra leucosticta Thuret, as interpreted by Hus, 

 1902, p. 199, pi. 20, figs. 1-3. Porphyra naiadum Anders., as interpreted 

 by Taylor, 1945, p. 133 as to Costa Rican examples only. 



Thalli saxicolous, or rarely epiphytic, usually 2.5-6 cm. high, dull 

 rose to purplish in color, consisting of a single blade from a small discoid 

 base, the blade commonly broadly reniform, usually broader than tall, 

 sometimes deeply lobed and lanceolate, cordate at the base, with a very 

 short stipe, monostromatic, 25-50 /t thick, of subcubical cells with a 

 single stellate chromatophore ; plants monoecious; spermatangia and 

 carposporangia in alternate streaks diagonal to the margin of the blade; 

 spermatia in packets of 64 according to the formulad, 1,1; carpospores 



a b c 



in packets of 8 according to the formula i , i, i. 



a b c 



Type: Holotype is Setchell 5161, May 29, 1900, in the Herbarium 

 of the University of California, Berkeley. An isotype is on sheet 55729 

 in HAHF. 



Type locality: Carmel Bay, California, on floating Gracilariopsis 

 sjoestedtii. 



Mexican distribution: Pacific Baja Calif. — D. 85, Cabo Col- 

 nett, Jan. (fertile) ; D. 9089, Islas San Benito, Apr. (a very small 

 example epiphytic on Phyllospadix with P. naiadum) ; D. 9821, South 

 Bay, Isla Cedros, Apr., D. 9151, Bahia Asuncion, Apr. (small, epiphytic 

 plants which differ by their spotty antheridial areas) ; D. 9345, Punta 

 Hughes, Isla Magdalena, May. Gulf of Calif. — D. 423, Punta San 

 Felipe, Feb. ; D. 335-40, Consag Rock, Jan. ; D. 982b, Isla Partida, Feb. 

 (fertile) ; D. 726, Isla Patos, Feb. (fertile) ; D. 495, Bahia Bocochi- 

 bampo, Feb.; D. 7246, Isla Danzante, Mar.; D. 7050, Isla Carmen, 

 Mar. 



