22 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 26 



Bahia Vizcaino, 37 m.; D. 20353 (Neushul), Bahia San Hipolito, 8 m. 

 A single dried collection from the northern Gulf of California, D. 185-40, 

 seems to be this species but is too poorly preserved for positive identifi- 

 cation. 



The frequent occurence from the basal cells of determinate geminate 

 ramuli of indeterminate branches of delayed or suspended development 

 is a character of probable significance in this species. 



Most of the Mexican specimens lack tetrasporangia and cannot 

 positively be distinguished from Antithamnion setaceum Gard. 



Antithamnion secundatum Gard. 



PI. 7, fig. 3 

 Gardner, 1927 b, p. 413. 



Thalli minute, 7-8 mm in extent, the lower parts, or sometimes 

 major parts of plant, prostrate and attached by slender, multicellular 

 rhizoids; primary axes about 60 /x, in diameter, of cells 1.5-2.0 diameters 

 long, frequently branched, the indeterminate branches without an 

 opposite ramulus, all axes otherwise clothed with paired, opposite, 

 determinate ramuli from the distal end of each axial cell; determinate 

 lateral branchlets 20-22 jx in diameter at the base, about 40 /x long, 

 of 8-10 cells, the basal cell subspherical, the others about 2 diameters 

 long, somewhat attenuated, the tips pointed, the outer ends more or 

 less recurved, especially in age, bearing adaxially 4-6 simple, outwardly 

 curved ultimate branchlets; basal cell often producing indeterminate 

 branches; gland cells absent; reproduction not seen in Mexican material; 

 tetrasporangia described as: "either on short (1-2 cells), diminutive, 

 fructiferous ramuli arising on the adaxial side and on the lower half 

 of the geminate ramuli, the upper half being occupied by the ultimate 

 ramuli, or sessile on the same and frequently on the same cell with an 

 ultimate ramulus, or sessile on the adaxial side of the ultimate ramuli, 

 75-85 i.i long, 60-64 /x broad;" carpogonia, cystocarps and antheridia 

 unknown. 



Type: Gardner no. 3525, December, in Herb. University of 

 California, Berkeley (296617). An isotype is in Herb. A. Hancock 

 Foundation. 



Type locality: Growing on floats in the harbor of San Diego, 

 California. 



Mexican distribution: Gulf of Calif. — A. H. F. St. 554-36 

 (D. 4367), March 8, 1936, Isla Angel de la Guarda, 20 m.; D. 6934a, 

 Canal de San Lorenzo, 14-26 m. 



Antithamnion sublittorale Setch. & Gard. 

 PL 7, fig. 2 

 Setchell and Gardner, 1937, p. 86, pi. 6, fig. 15; Dawson, 1944, p. 313. 



Thallus minute, consisting of a sparingly branched creeping axis 



