108 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



rather straight, unicellular rhizoids ; perithallus consisting of ( 1 ) a thick, 

 calcified layer of large, irregularly shaped cells with conspicuous inter- 

 cellular spaces and rather sparse cytoplasmic contents, these rounded to 

 elongate-quadrangular and mostly taller than broad, 25-45 /a in greatest 

 diameter, reduced in size upward, and (2) a thinner, non-calcified, sur- 

 face layer of 4-7 tiers of small cells 6-7 fi wide, 10-14 /x tall, except the 

 outermost 1-2 tiers which are usually flat and only 4-5 ju, tall; larger, 

 rounded heterocysts frequent among the smaller, superficial cells, about 

 12-18 fi in diameter; tetrasporangial nemathecia small, about 80-90 [x 

 deep, with slender paraphyses terminated by about 2 subspherical cells 

 united in a gelatinous surface matrix; tetrasporangia ovoid, 55-72 ju, 

 long, 22-35 fi wide. 



Type: Holotype destroyed in Berlin in 1945. 



Type locality : Tami Island, New Guinea. 



Mexican distribution: Revillagigedo Archipel. — ^Taylor 34-41, 

 dredged from 37 meters, Bahia Braithwaite, Isla Socorro, Jan. 



With the loss of the type of this species originally described from 

 sterile material, one must rely heavily upon the work of Weber van Bosse 

 for an interpretation of this plant. Although Taylor's specimen does 

 not show the "zones d'accoisement" indicated in Weber van Bosse's 

 figure, it seems to agree in all other essential details with the East Indian 

 plant, including the presence of the cortical heterocysts. 



Peyssonelia clarionensis Taylor 

 Plate 10, fig. 10; Plate 11, figs. 10-11; Plate 33, fig. 2 



Taylor, 1945, p. 168. 



Thalli closely crustose except at the very margin, to 2 cm. broad or 

 more, 150-220 ju, thick, chalky pink when dry, firmly calcified below and 

 brittle, attached first by numerous unicellular rhizoids ; hypothallus cells 

 mostly 25-30 /x long, 14-16 (20) /x wide in surface view, 20-25 /x high, 

 supporting ascending and then vertical, once- or twice-forked rows of 

 perithallus cells; perithallus cells more or less rectangular in section, 

 variable in length but mostly longer than broad in mid-parts of rows, 

 those of the last 2-3 tiers flat, 10-13 ju, broad; tetrasporangial nemathecia 

 scattered, small 0.5-0.8 mm. in diameter, prominently elevated, to 120 

 /x thick; paraphyses slender, slightly clavate, branched, of 5-6 cells with 

 narrow lumena, the upper ones short, the lower much elongated; tetra- 

 sporangia elongate-ovate, 85-133 /x long, 45-60 /a wide. 



