58 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 26 



and distantly dichotomously, divergently branched, corticated only at the 

 nodes; apices circinate; nodal cortex 40-60 p. long, of irregularly ar- 

 ranged, small angular cells, bearing a whorl of 5 6, usually 3-celled, non- 

 deciduous, stout spines 30-50 /x long with sharp, usually hooked tips, the 

 hook directed basally; internodes elongating early, becoming 100-250 ju. 

 long in older filament parts; nodes occasionally with slender, accessory 

 rhizoids; secondary cortical expansion essentially absent; reproduction 

 not seen. 



Type: E. Y. Dawson 3706, December 20, 1946, in Herb. A. 

 Hancock Foundation 



Type locality: Intertidal, Mira Mar, south of San Bias, 

 Nayarit. 



Mexican distribution: Nayarit — D. 10874, Mira Mar. 



Ceramium horridum Setch. & Gard. 

 PL 23, fig. 4 



Setchell & Gardner 1924, p. 777, pi. 26, fig. 49-50, pi. 79; Dawson 1944, p. 318; 

 Dawson 1950, p. 116. 



Thalli 6-8 cm. high, completely corticated throughout, dichotomously 

 branched, the branches gradually attenuated from about 500 jx in the 

 lower parts, the tips at first forcipate, ultimately terminating in divari- 

 cate, unicellular spines, such spines also terminating short lateral 

 branchlets; lower parts more or less abundantly provided with short 

 lateral branchlets tending to be whorled at the nodes; cortical cells 

 angular, tending to be arranged in longitudinal rows; tetrasporangia 

 immersed without definite order in fertile bands at the nodes of main 

 axes and of short lateral branchlets, about 30 jx in diameter; sexual 

 plants not seen. 



Type: Marchant 91, May, in Herb. University of California, 

 Berkeley. 



Type locality: Cast ashore, Guaymas, Sonora, Mexico. 



Mexican distribution: Gulf of Calif.— D. 256-40, Puerto Re- 

 fugio, 12-22 m.; D. 427-40, 430-40 Isla Pond; D. 143-40 Isla Tiburon, 

 4-32m.; D. 6965 (AHF Sta. 526-30) Los Mangles, Isla Carmen; D. 

 6926 Isla Espiritu Santo. 



Ceramium howellii Setch. & Gard. 

 PI. 21, fig. 1; PI. 22, fig. 1 

 Setchell & Gardner 1937, p. 88, pi. 6, fig. 14. 



Thalli up to 15 mm. high, 180-350 fx in diam., attached by rhizoids, 

 partly prostrate and partly erect, with relatively sparse secund branching 

 from the prostrate filaments, with irregularly alternate, sparse, mostly 

 short branches from the erect filaments; growing apices tending to be 

 adaxially curved to hooked, narrowly tapered; axes completely corticated 

 throughout with no superficial indication of nodes; corticating cells 



