84 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



Gelidiella stichidiospora sp. nov. 

 Plate 12, figs. 4-5 



Frondes 1-2 mm. altae, conchicolae, velvetum similis; rami's erectis, 

 cylindricis vel compressis, 40-60 fi diam. ; apicibus acutis ; tetrasporangiis 

 30 ju, latis, in stichidiis terminalibus, lente tumidis, in serie quadruplicis 

 regularis ordinatis. 



Thalli conchicolous, forming a velvet-like turf 1-2 mm. thick on 

 the surface of shells of living Haliotus, consisting of a more or less 

 compacted basal stratum of prostrate branches attached by groups of 

 modified, elongated cortical cells from which numerous erect branches 

 arise; erect branches simple or once (twice) branched, 40-60 /a in dia- 

 meter, terminally acute, consisting usually of 3 concentric cell layers, the 

 outermost, cortical layer of irregularly quadrangular cells 8-9 /x in dia- 

 meter, the inner of cells of similar diameter but to about 35 /t long; 

 tetrasporangia borne in more or less determinate terminal stichidia 20-50 

 /A long or more; stichidia cylindrical, about 70 ju, in diameter, often aris- 

 ing from branch tips as slender as 25 /x and appearing swollen ; sporangia 

 about 30 ju, in diameter, borne in four ranks arranged in regular layers 

 which mature successively toward the apex; sexual reproduction un- 

 known. 



Type : Holotype is Dawson 10543, Oct. 30, 1951, in vial 2691 and 

 in tray 56 in HAHF. 



Type locality: On shells of living Haliotus j Punta Norte, Isla 

 Cedros, Baja California, Mexico. 



The more or less indeterminate terminal stichidia with sporangia 

 arranged in four regular ranks and in uniform horizontal layers, and 

 the velvet-like colonial habit of this small species are distinctive, 



Gelidiella ? refugiensis Dawson 



Dawson, 1944, p. 263, pi. 43, figs. 4-6. 



Thalli 1-1.5 cm. high, subcylindrical to compressed, 150-300 (x in 

 diameter; basal parts unknown; branching mostly distichous but irregu- 

 lar, at intervals of 0.6-3 mm., most approximate in upper parts, some- 

 times with a group of polystichous branches at the tip of an axis ; apices 

 acute, with a distinguishable apical cell ; structure consisting of a medul- 

 lary core of slender, elongated, thick-walled cells and a cortex and sub- 

 cortex of about 3 layers of cells ; rhizoidal filaments absent ; reproduction 

 apparently by large monospores? 20-50 fx. in diameter, borne in cavities 

 in the cortex of short, acute terminal branchlets which are not conspic- 

 uously swollen. 



