220 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



cuticle which remains intact upon crushing the specimen, the filaments 

 themselves however also moderately firmly laterally united, not easily 

 separated ; reproduction not seen. 



Ecuador: Archipielago de Colon, forming a smooth blackish crust 

 on volcanic rock, I. Bartolome near I. San Salvador, no. 34-342, 23 Jan. 

 1934. 



These specimens had more of the firmness of Hildenbrandia than of 

 Petrocelis, but are rather thick and the filaments did separate, althougR 

 reluctantly, under pressure. Lacking reproduction, it is not thought best 

 to attempt to give a name to these plants. They do not show the anasto- 

 moses of P. franciscana Gardner (1917, p. 391), the filaments branch 

 and rest on a thick hypothallus, so differing from P. haematis Hollenberg 

 (1943, p. 575). 



Petrocelis sp. 



Plants encrusting, of moderate thickness, light brownish red, 2-3 cm 

 diam. ; basal layer of radiating branched filaments; erect row^s of cells 

 about 16 {x diam., the total thickness to 350 /x, the tip cells conical; readily 

 dissociating with pressure after decalcification ; reproduction not seen. 



Mexico: Is. Revilla Gigedo, on coralline fragments dredged from 

 sta. 134 at 56 meters off I. Clarion, no. 34-74B, 5 Jan. 1934. 



Sebdeniaceae 



Thallus flat, foliaceous, cleft or lobed ; structurally showing a medulla 

 of filamentous construction and a dense cortex with larger cells within, 

 smaller without; sporangia tetrapartite, scattered in the cortex; cysto- 

 carps protuberant, cells elongating to form a subfilamentous pericarpic 

 investment around the carpospore mass, with a group of nutritive cells at 

 the base of the mass of gonimoblasts, of which most of the cells form 

 carpospores. 



SEBDENIA Berthold, 1882 



Sebdenia rubra n. sp.^^^ 

 Plate 73 



Plants to 10 cm tall, dark rose red, nitent when dry, membranous; 

 from a very small holdfast an ovate to suborbicular or subreniform blade 

 arising, with or without a very short stalk, simple or cleft nearly to the 



133 Sebdenia rubra n. sp. — Planta ad 10 cm altitudine, foliacea, membranacea 

 nitens cum sicca est, stipite minuta, lamina ovata ad subreniformem, simplici aut 

 in 2-3 segmentis similaribus divisa, margine integro ad paululum undulatum, 

 crass, (madefacta) ad 150-175 \.i; medulla praebente filamenta parietes tenues 

 habentia et filamenta pauca, perspicuissima, refractivissima, sparse anastomosantia; 

 tetrasporangiis 9-11 |.i diam., 15-18 \.i long.; cystocarpis multis, 0.1-0.2 mm diam., 

 paululum proicientibus. Planta tvpica in loco dicto I. Santa Maria, Ecuador, legit 

 W. R. Taylor no. 34-384, 29 Jan." 1934. 



