NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 67 



of a narrow inner ring of larger cells and, on either side, of an outer ring 

 or irregularly arranged small angular cells less than 10 /x in maximum 

 diameter; tetrasporangia cruciate, ovate, about 40 /x in length, borne 

 verticillately within prominently swollen involucres which develop 

 acropetally from the closely juxtaposed distal nodal bands of the erect 

 axes; terminal fertile areas to 220-250 /x in diameter, resembling those 

 of Equisetum in form. 



Type: E. Y. Dawson 13620a, August 19, 1955, in Herb. Bernice 

 P. Bishop Museum, Honolulu. 



Type locality: Growing within tufts of Ectocarpus breviarticu- 

 latus near the margin of the seaward reef opposite EMBL, Parry Island, 

 Eniwetok. 



Mexican distribution: Revillagigedo Arch. — D. 12074, Isla San 

 Benedicto. Gulf of Calif.— D. 735-40, Isla Turner off Isla Tiburon. 



Ceramium viscainoense Daws. 



PL 27, fig. 1-2 

 Dawson 1950, p. 120, pi. 1, fig. 1-3. 



Thallui 15-25 mm. high, tufted, saxicolous, attached by massed and 

 coalesced short rhizoids which in mature plants form a spongy disc, 

 consisting of several to many dichotomously branched axes arising from 

 the base; older branches 400-500 /x in diam., catenately constricted at 

 the nodes, gradually reduced in diameter above and the constrictions less 

 prominent; secondary proliferous branches multifarious, short, increas- 

 ingly abundant and more congested above; ultimate branches divergent, 

 non-forcipate, acute; cortex continuous throughout, primarily of irregu- 

 larly disposed small angular cells and a few larger cells at the junction 

 of the rotund axial cells, generally thin or incomplete over the bulging 

 midparts of the central axial cells, the longitudinally arranged, small, 

 mostly elongated cells of young segments becoming in part increasingly 

 longer or even filamentous as secondary, acropetal and basipetal cortical 

 growth progresses; tetrasporangia 30-35 /x in diam., completely 

 immersed in the cortex ; cystocarps surrounded by 3-5 involucral branch- 

 lets. 



Type: E. Y. Dawson 1430, April 13, 1946, in Herb. A. Hancock 

 Foundation (5225). 



Type locality: Intertidal rocky shore, Punta Santa Rosalia, Baja 

 California, Mexico. 



Mexican distribution: Known only from the type. 



Ceramium zacae Setch. & Gard. 

 PL 26, fig. 4-6 

 Setchell & Gardner 1937, p. 89, pi. 8, fig. 22a-c; Dawson 1945. p. 62: 

 Dawson 1950, p. 134, pi. fig. 27-28; Dawson 1957a, p. 8; Dawson 1959, p. 30: 

 Dawson, Neushul & Wildman 1960a, p. 24. 



Thalli epiphytic, attached to the host by short, branched, penetrating 



