NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 37 



last several orders; cystocarps binate, the lobes somewhat irregularly 

 heart-shaped or triangular. 



Type: A Borgesen collection, March, probably in the Botanical 

 Museum of Copenhagen. 



Type locality: Epiphytic on Gracilaria, 15 fms. Cruzbay, 

 Virgin Islands. 



Mexican distribution: Pacific Baja Calif. — D. 8256 (48-56 m.), 

 D. 8277 (76-100 m.), D. 8280, D. 8422 (48-56 m.), D. 8431, 8434 

 (48-56 m.) Isla Guadalupe. 



The Guadalupe Island specimens show such extraordinary resem- 

 blance to B0rgesen's West Indian plant that there seems little question 

 of their identity and of the occurrence of this genus, heretofore 

 unreported in the Pacific. 



Aglaothamnion brodiaei (Harv.) Feldmann-Maz. 

 PL 12, fig. 4-5 

 Feldmann-Mazoyer 1940, p. 452, fig. 177. Callithamnion brodiaei Harvey, in 

 Hooker 1833, p. 340; Rosenvinge 1923-24, p. 313, fig. 224-228. Callithamnion 

 byssoides as interpreted by Setchell & Gardner 1930, p. 167, and by Dawson 

 1960, p. 50. 



Plants epiphytic, 1 cm. high or less, consisting of several erect, 

 multifarious axes from a rhizoidal attachment; erect axes 100-140 fi in 

 diam. at the base, lightly corticated near the base by descending, 

 appressed filaments, the cells mostly 1.5 diameters long, gradually 

 reduced to the ultimate branchlets which are 6-10 ja in diam.; branching 

 attenuate, spiral, of several orders, the ultimate ones of 1-4 cells, 2-4 

 diameters long, commonly terminating in a hair, longer in sterile 

 plants; gland cells absent; tetrasporangia sessile, subspherical, about 

 60 fx in diam. including the thick envelope, adaxial on the upper 

 branches; spermatangia in spreading adaxial tufts along upper branch- 

 lets; gonimoblast consisting of two large, rounded to cordiform gonimo- 

 lobes and two smaller ones. 



Type: A collection by Mr. Brodie, probably in the Harvey 

 Herbarium, Trinity College, Dublin, Ireland. 



Type locality: Forres, England. 



Mexican distribution: Pacific Baja Calif. — Mason 89 "on eel 

 grass," D. 4089 (20-30 m.), D. 19249 (C. Limbaugh, on Codium), 

 D. 19253 (38 m.), Isla Guadalupe. 



Comparison of the abundantly fertile collections from Isla Guada- 

 lupe with Feldmann-Mazoyer's account of Aglaothamnion reveals that 

 this plant had best be assigned here in keeping with the characters of 

 the gonimoblast and abundant hairs on the branch tips. Assignment of 

 these specimens previously to Callithamnion byssoides had not taken 

 these features into account. All of these, however, are smaller and much 

 less corticated plants than the relatively coarse specimens originally 



