NO. 10 DAWSON : MARINE ALGAE, GULF OF CALIFORNIA 283 



Prionitis abbreviata S. & G. 



Setch. & Card., 1924, p. 785, pi. 25, fig. 39, pi. 50b. 



This plant is well illustrated by Setchell and Gardner and may be 

 identified thereby. Difficulty may be encountered in distinguishing young 

 stages from those of Prionitis Sternbergii, and even in adult plants there 

 may be some confusing similarities, but in general the distinctions pointed 

 out under that species may be relied upon. 



J. 53e, on rocks, San Esteban Island, April; D. 453, Feb.; D. & R. 

 3404, Punta San Pedro, Guaymas, Dec. ; D. 490, Catalina Bay, near 

 Guaymas, Feb. 



Prionitis mexicana sp. nov. 

 Plate 67, Fig. 2 



Frondes 8-12 cm. altae, e disco basali parvo, teretes usque ad leviter com- 

 pressae, .7-.8 mm. diam., irregulariter pinnatae; ramis longitudine variabilibus 2 

 mm. usque ad 6 cm. longis, diametro ea axis primae equatis, apicibus semiacutis; 

 structura generis typica. 



Fronds 8-12 cm. high, attached by a small discoid holdfast from which 

 arise several slender, terete, to slightly compressed main axes, .7-. 8 mm. 

 diam. ; branching irregularly pinnate, the branches of varying length, 

 some short, 2-4 mm., but often long, 2-6 cm., of about the same diameter 

 as the main axis or not conspicuously smaller ; apices semiacute, not much 

 attenuated ; structure typical of the genus ; reproduction unknown. 



Type: D. 628, middle littoral on rocky reef, San Jose del Cabo, 

 Feb. 16, 1940. Herb. AHF no. 31. 



D. 29, dredged in 36-50 meters, Santa Maria Bay, outer coast of 

 Lower California, Jan. 19, 1940. 



This species is highly distinctive among the Prionitis plants of our 

 region. It resembles in its slenderness P. filiformis of the central Califor- 

 nia coast, but differs markedly in its long-pinnate branching. 



Only one of the two localities for Prionitis mexicana is strictly within 

 our area, this plant probably being more abundant on the outer coast of 

 southern Lower California than within the limits of the Gulf. 



Prionitis guaymasensis sp. nov. 

 Plate 66, Figs. 1, 2 



Frondes usque ad 7 cm. altae, rigidae, cartilagineae, a disco parvo affixae; 

 a disco axes paucae primae assurgentes, compressae, 1.5-2 mm. latae, per occa- 

 sionem furcatae, ramis raultis pinnis indutis; pinnis pleruraque angulis rectis emer- 

 gentibus, frequenter proxime aggregatis, basim attenuatis, supra medium 0.7-1 mm. 

 latissimis, longitudine variabilibus (5-18 mm.) per occasionera furcatis aut ramo- 

 sis,- apicibus semiacutis sed non attenuatis. 



