60 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 26 



11031-11033, Ensenada de San Francisco. Revillagigedo Arch. — D. 

 12049, Isla San Benedicto. Oaxaca — D. 3815, 3819, Salina Cruz. 



This species has been reported from Viet Nam and from several 

 localities in the central Pacific. The material from Ensenada de San 

 Francisco is luxuriant and is the first to show the ultimate development 

 of the whorled tetrasporangia in the tumid nodes after an initially abax- 

 ial development. 



There is considerable resemblance between our plants and Easter 

 Island material assigned by H. E. Petersen to Ceramium cruciatum Col. 

 & Herv. (B0rgesen 1924, p. 297, fig. 37). 



Ceramium obesum Daws. 

 PL 22, fig. 5-6 

 Dawson 1950, p. 119, pi. 1, fig. 7-9. 



Thalli prostrate, creeping, growing over themselves and other 

 small algae and debris, attaching by masses of small rhizoids produced 

 from all contacting surfaces, very course, cylindrical, 900-1100 jx in 

 diam., with axes 20-22 mm. long, completely corticated throughout, 

 abruptly reduced at the apices to short, coarse, strongly forcipate tips; 

 primary branching dichotomous, infrequent; secondary branching ir- 

 regular, frequent, consisting mostly of very short branchlets with 

 strongly incurved tips; cortex very thick, completely covering the axes, 

 consisting of an inner layer of thick- walled rotund cells 25-100 /x in 

 diam. adjoining the central axial cells which are about 400 ll in diam., 

 and an outer layer of densely packed small anticlinally elongated cells 

 15-25 jx long by 5-9 it wide; reproduction not seen. 



Type: E. Y. Dawson 964, Feb. 21, 1946, in Herb. A. Hancock 



Foundation (5279). 



Type locality: Intertidal rocky shore, Bahia Agua Dulce, Isla 

 Tiburon, Sonora, Mexico. 



Ceramium ornatum Setchell & Gardner 

 PL 24, fig. 2 

 Setchell & Gardner 1930, p. 172; Dawson 1950, p. 137, pi. 2, fig. 10. 



"Fronds approximately 4 cm. high, the main axes approximately 

 [300-450] [x in diam., sparsely and dichotomously branched with occa- 

 sional proliferous ramuli and all tapering gradually toward the apices, 

 slightly swollen at the nodes; cells of the axial filament cylindrical, 1-1.5 

 times as long as broad; nodal band extending beyond the surface of the 

 axial filament, relatively narrow, equally distributed above the node, 

 composed of one whorl of deep-seated, large cells cutting off above 

 and below usually one whorl each of smaller, more or less globular 

 cells, these in turn giving rise to numerous, small, angular, surface 

 cells, irregularly placed and giving rise to numerous, long, narrow, 



