NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 29 



Type locality: Dredged in 15-30 m., Farnsworth Bank, Santa 

 Catalina Island, California. 



This species has not yet been detected in Mexico, but almost 

 certainly it will be found there when sublittoral areas similar to 

 Farnsworth Bank are more extensively explored. 



Callithamnion compactum sp. nov. 

 PI. 9, fig. 3 



Thalli epiphytici penicilla compacts rotundata 1-2 mm. alt. formantes, ex 

 axibus brevibus congestis, e disco communi multicellular! orientibus, con- 

 stantes; axes erecti ecorticati ad basim 30 /t diam., supra diametro, nisi ad 

 cacumina, vix reducti cellulis 1.2-2.0 plo longioribus quam latae; axes princi- 

 pales ramos unum vel aliquot primarios breves habentes, omnes ramulis 

 obtusis incurvatis plerumque simplicibus (aut semel furcatis) 150-200 fi long., 

 20-25 n diam. vestiti; ramuli e cellulis aliquantulum longioribus quam latae 

 compositi, alterni (interdum oppositi), spiraliter ordinati; glandicellulae 

 nullae; tetrasporangia multa, seriata (4-6) sessilia in ramulis adaxialia ca. 

 35 (i long., 30 fi lat; reproductio sexualis ignota. 



Thalli epiphytic, forming compact, rounded tufts 1-2 mm. high, 

 consisting of densely congested short axes from a common multicellular 

 disc; erect axes ecorticate, 30 ll in diameter at the base, scarcely 

 reduced in diameter above except at the tips, the cells 1.2-2.0 diameters 

 long; main axes with one or a few short primary branches, the whole 

 clothed with mostly simple (or once forked) incurved, blunt ramuli 

 150-200 ju, long, 20-25 fi in diam., of cells a little longer than broad; 

 ramuli alternate (occasionally opposite) spirally arranged; gland cells 

 absent; tetrasporangia abundant, seriate (4-6), sessile, adaxial on the 

 ramuli, about 35 li long, 30 ll broad; sexual reproduction unknown. 



Type: Holotype is E. Y. Dawson 9179, April 28, 1950, in Herb. 

 A. Hancock Foundation. An isotype slide is in Herb. Beaudette 

 Foundation. 



Type locality: Epiphytic on Prionitis delicatula, intertidal, 

 Bahia Asuncion, Baja California, Mexico. 



Additional material: D. 13419, on the same host, intertidal, 

 Pacific Isla Magdalena, Baja California, Mexico. A sterile plant of 

 similar characters, possibly referable here, is D. 3499, vicinity of 

 Guaymas, Sonora, Mexico, epiphytic on Grateloupia. 



The compact habit of numerous axes from a spreading disc is 

 distinctive as well as the subsimple, spiral, incurved, blunt ramuli. 



Callithamnion endovagum Setch. & Gard. 

 PL 8, fig. 5 

 Setchell & Gardner 1924, p. 771, pi. 28, fig. 62; Dawson 1953, p. 19. 

 Acrochaetium grateloupiae Dawson 1950, p. 1953, fig. 22-23. 



Thalli partly endophytic, the endophytic filaments intercellular, 

 growing between the cortical cells and parallel to the surface of the host, 

 7-11.5 ll in diam.; erect portions 4-12 cells long, to 250 [i high, with 



