NO. 8 DAWSON : A REVIEW OF THE GENUS RHODYMENIA 141 



are tentatively placed under R. palmettiformis do show occasional branch- 

 ing of the stipe in its upper parts, a feature which would seem to place 

 them in Dendrymenia. The aspect of the plants, however, is not dendry- 

 menioid in the sense herein interpreted. 



(33) RHODYMENIA DIVARICATA sp. nov. 



Plate 23, Fig. 31 



Frons 4-5 cm. alta, estipitata, e basi in dichotomiis irregularibus expansis, 

 segmentis late divaricatis, angulis latis; segmentis vulgo 2-3 mm. latis, brevibus, 

 ultimis brevissimis, lobiformibus, apicibus rotundatis, plus minusve 250 \i crassis, 

 superficie corticis cellulis parietibus tenuibus leviter angulatis composita; tetra- 

 sporangiis cystocarpiisque nondum visis. 



Fronds 4-5 cm. high, essentially stipeless, expanding from the base 

 into irregular dichotomies, the divisions spreading, with wide axillary 

 angles ; segments mostly 2-3 mm. broad, short, the ultimate segments very 

 short, lobelike, with rounded apices, about 250 \i thick, with a cortex of 

 thin-walled, slightly angular cells as seen in surface view. Tetraspores 

 and cystocarps unknown. 



Morphologically this species is nearest to R. calif ornica, from which 

 it is distinguished by its strongly divaricate nature, by the less regular 

 dichotomies, and by the irregularly lobed appearance of the ultimate 

 segments. 



Type. — Dredged in 2-3 fms., mud bottom, Guaymas Bay, Sonora, 

 Mex., January 22, 1940, E. Y. Dawson 53 of Allan Hancock Expedition 

 to the Gulf of California — 1940; Herb. Allan Hancock Foundation, 

 AHFno. 1. 



Other specimens from sand and coralline bottom in 6-11 fms. off 

 Mejia IsL, Puerto Refugio, Angel de la Guardia Island, Gulf of Calif., 

 E. Y. Dawson 257, Jan. 28, 1940. 



(34) RHODYMENIA ROSEA sp. nov. 



Plate 24, Figs. 32-33 

 Frons erecta usque ad 7 cm. alta, sessilis, e disco simpHci oriens, e basi directe 

 expansa, laete rosea; ramificatione primaria irregulariter dichotoma, marginibus 

 laminarum sparse denticulatis et in segmentis prolificantibus, iisdem basim angustis 

 et frequenter dichotomis; segmentis 2-3 mm. latis, apicibus rotundatis, plus 

 minusve 100 n crassis, corticibus acute delimitatis; cellulis corticalibus superficie 

 parietibus tenuibus et acute angulatis. Tetrasporangiis cystocarpiisque nondum 

 visis. 



Fronds bright rose, erect to 7 cm. high, nonstipitate, from a simple 

 holdfast, expanding directly from the base; primary branching irregularly 



