NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 97 



Myriogramme divaricata Dawson 

 PL 40, fig. 5; PL 42, fig. 2 

 Dawson 1944, p. 323, pi. 47, fig. 5 



Thalli to 3 cm. high, membranous, from a small, semi-rhizoidal 

 holdfast below a solid, stipitate base 1 mm. or less in extent; 

 blades proliferous only from lowest parts, abruptly divaricately dichoto- 

 mously branched, lacking a midrib, with broad, short, veinless, mono- 

 stromatic segments; axils of segments rounded, not angular; apical mar- 

 gins multilobate, the lobe often appearing truncate; growth from apical 

 margins, without a terminal cell; tetrasporangia in small sori scattered 

 through middle and upper portions of blades; sexual plants unknown. 



Type: Dawson 181-40, Jan. 28, 1940, in Herb. A. Hancock 

 Foundation (59). 



Type locality: Dredged in 22-44 m., Puerto Refugio, Isla Angel 

 de la Guarda, Gulf of Calif. 



Known only from the type. 

 Working Key to the North Pacific Species of Cryptopleura 



1. Thallus diminutive, the free branches under 2 cm. long 2 



1. Thallus larger, the free parts 3-25 cm. long 4 



2. Thalli epiphytic, largely prostrate, the free branches mostly 



rounded and lobed, less than 1 cm. long, to 3 mm. broad 



C. corallinara 



2. Thallus saxicolous, or apparently so 3 



3. Branches free, dichotomously branched, very narrow (1 mm. 



wide) ; reproduction unknown C. dichotoma 



3. Blades superimposed, prostrate with only the tips free, broadly 



lobed (4-6 mm.) ; tetrasporangial sori on terminal lobes 



C. imbricata 



4. Upper segments narrow, linear, only about 1 mm. broad .... 

 C. hayamensis 



4. Upper segments mostly 4-10 mm. broad or more 5 



5. Thalli epiphytic or usually so; tetrasporangia borne in crisped 



marginal proliferations forming a fringe on mature segments .... 



C. crispa 



5. Thalli usually saxicolous or at least not primarily epiphytic .... 6 



6. Thallus thin and papery, monostromatic in upper parts 

 except at veins C. spatulata 5 



6. Thallus not so thin, mostly or wholly plurostromatic 7 



Two southeastern Pacific species of Cryptopleura are known from Peru, both 

 of them monostromatic between the veins. C. cryptoneurum (Mont.) Taylor 

 resembles both C. spathulata and C. violacea. It has the sori on the main blades 

 forming linear marginal bands extending the length of several segments, the 

 same as in some specimens of C. violacea. C. peruviana Taylor seems to be 

 more like C. lobulifera with a lobing and ruffling of midparts of the thallus 

 and the tetrasporangial sori on these marginal ruffles or lobules. 



