NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 53 



Type: Marchant 48b, May, in Herb. University of California, 

 Berkeley. 



Type locality: Floating among other algae, Eureka, near La Paz. 



Mexican distribution: Pacific Baja Calif. — Hubbs 12/7/46, 

 D. 8524, Isla Guadalupe; D. 8792, Bahia San Quintin. Gulf of Calif.— 

 D. 3480, Bahia Empalme; D. 857, Isla Jorge; D. 10991, 10988, Bahia 

 de San Francisco; D. 18780, D. 18769, Puerto Escondido; D. 10894, 

 Bahia Topolobampo. 



This is apparently a species of infrequent occurrence and has been 

 confused and redescribed as C. avalonae from southern California 

 because of the disjunct distribution and variation of the cortical-band 

 morphology between younger, smaller and more luxuriant plants. The 

 abaxial, usually caudate tetrasporangia and the pendant appearance of 

 the larger, lower cells of younger cortical bands are distinctive. The 

 Setchell & Gardner illustrations of the cortical bands of the type were 

 not accurately drawn and do not indicate the distinctive cell arrange- 

 ments. 



Ceramium clarionense Setch. & Gard. 

 PI. 18, fig. 5-6 

 Setchell & Gardner 1930, p. 170, pi. 7, fig. 25-27; Dawson 1950, p. 134, 

 pi. 4, fig. 29; Dawson 1957, p. 8. 



Thalli to 1 cm. high, partially creeping and attached multicellular 

 rhizoids, often producing a green iridescence in life; erect parts 

 160-250 ju, in diam., regularly dichotomously branched with strongly 

 circinate apices; cells of central axis slightly longer than broad below, 

 diminishing in length upward; cortication of variable extent, the inter- 

 nodes sometimes so narrow above as to be little more than lines, 

 commonly 40-60 p. above, lengthening to 150-200 /x below ; cortical bands 

 usually a little more than 1/2 as long as wide, truncate above and 

 below, sometimes becoming tumid in lower parts, consisting of a central 

 inner row of rotund cells 15-18 jx in diameter and an outer layer of 

 irregularly arranged, more or less angular cells mostly about 10 fi in 

 maximum dimension, provided, external to the cortical cells, with small, 

 deeply staining globules ("gland cells") and sometimes also with short 

 hairs; tetrasporangia numerous, emergent, usually naked, scattered 

 adaxially or all the way around the node without cortical modification; 

 spermatangia surrounding the nodes, 1.5 /x in diameter; cystocarps borne 

 in the axils of the dichotomies, naked, variously lobed. 



Type: H. L. Mason, 75, June, in Herb. California Academy of 

 Sciences (173620) 



Type locality: Growing on Codium, Isla Clarion, Revillagigedo 

 Arch., Mexico 



Mexican distribution: Pacific Baja Calif. — D. 8609, 8377, Isla 

 Guadalupe; D. 1393, Desembarcadero de Miller; Williams 5/14/46, 



