NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 59 



± angular, (4) -7-12 /j. in diam., without definite arrangement, essen- 

 tially in a single layer; central filament of large, cylindrical cells 

 tending to be shorter than broad; tetrasporangia completely embedded, 

 numerous, irregularly scattered but aggregated in ± distinct bands cor- 

 responding with the nodes of both main and lateral branches, the fertile 

 axes to 600 ft in diam; spermatangia covering upper part of the thallus; 

 cystocarps lateral, surrounded by several clasping involucral branches 

 (modified from Setchell & Gardner). 



Type: J. T. Howell 379, June 2, in Herb. California Academy 

 of Sciences (236527). 



Type locality: On rocks, southeast side of Narborough Island, 

 Galapagos Archipelago. 



Mexican distribution: Pacific Baja Calif— D. 8266 (65-75 m.), 

 D. 8425 (45-55 m.) Isla Guadalupe. Gulf of Calif.— D. 6992, Bahia 

 Salinas, Isla Carmen (2-30 m.). 



These specimens, though sterile, are somewhat larger and more 

 luxuriant than the type, but otherwise correspond well with the Gala- 

 pagos material. Setchell and Gardner describe the tetrasporangia as 

 without definite order in somewhat swollen lateral branchlets. In the 

 luxuriant Bahia Salinas specimen the tetrasporangia are embedded at the 

 nodes in both main and lateral branchlets, forming fairly distinct bands, 

 but irregularly scattered within the bands. 



Ceramium mazatlanense Daws. 

 PL 23, fig. 1-2 

 Dawson 1950, p. 130, pi. 2, fig. 14-15; Dawson 1954a, p. 6. 



Thalli epiphytic, 3-4 mm. (up to 1 cm.) high, attached by rhizoids 

 from the ventral surface of a prostrate, basal part of a filament; erect 

 filaments 90-100 (150) /x in diam., rather irregularly dichotomously 

 branched, corticated only at the nodes, without secondary cortical 

 expansion; apices forcipate, sometimes circinate; cortical band very 

 short, 25-30 //. long, consisting of angular cells 7-25 /x in greatest diam., 

 the largest below and beneath, often bearing numerous fine hairs; in- 

 ternodes elongated below, sometimes to 200 (i; tetrasporangia borne in 

 prominently projecting, abaxial, secund cortical involucres, solitary or in 

 groups of 2-3 at the nodes, sometimes later whorled and the tumid nodes 

 appearing catenate, about 35 fi in diam.; spermatangia in low, adaxial 

 and abaxial pulvinate masses at the nodes, later partially or completely 

 encircling them; cystocarps not seen. 



Type: E. Y. Dawson 3606, Dec. 8, 1946, in Herb. A. Han- 

 cock Foundation (48798). 



Type locality: Epiphytic on Codium. Mazatlan, Sinaloa, Mexico. 



Mexican distribution: Gulf of Calif. — D. 657-40, near Kino; D. 



