NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 81 



character separating them from P, capillaceum." Indeed, P. tenuis of 

 Japan appears to be quite indistinguishable from the usual form of P. 

 pyramidale as understood in California, while the congestedly branched 

 form also occurs in Japan where it is known under the name P. densa. 

 Now, with the reduction of P. okamurai under P. pyramidale , it is equal- 

 ly difficult to point out any clear-cut differences between P. pyramidale 

 and P. capillacea. It is not unlikely that all of these names may be de- 

 stined for combination as representatives of one polymorphic species, 

 but it must be left to a monographer of the group to decide whether and 

 how the north Pacific plants may be distinguished from the Mediter- 

 ranean P. capillacea, and whether the Australian plants currently re- 

 cognized under the latter name are in fact identical with the European. 

 From a comparison of Pacific North American and Australian-New 

 Zealand material, it seems probable that the plants from these areas are 

 conspecific. 



There remains one other Mexican Pterocladia to be considered: P. 

 mexicana Taylor. Several topotype collections of this plant including all 

 reproductive phases, are at hand from Isla Magdalena. All of these fall 

 within the range of variation of P. pyramidale and show that the type 

 represents merely a coarse, less-flattened-than-usual form of that species. 



Gelidiella ligulata sp. nov. 

 Plate 6, figs. 3-5 



Thallis 1.5-4 cm. altis, erectis, primarie baud ramificatis, laminis 

 ligulatis e ramis basalibus, subcylindricis, implicatis, repentibus, pene- 

 trabilibus; laminis 800-1300 /a latis, 150-200 \x. crassis, decrescentibus 

 ad margines, post maturitatem ramulas pinnatas spissas, deciduas ad vel 

 prope extremitates parientibus; filamentis rhizoideis absentibus. 



Thalli 1.5-4.0 cm. high, consisting of erect blades 1.0-3 cm. high 

 from irregularly branched, creeping, entangling, subcylindrical basal 

 parts 400-500 /i in diameter growing around and partially penetrating 

 small saxicolous sponges, mollusks, corallines and debris ; erect blades at 

 first unbranched, ligulate, gradually expanded and flattened from the 

 subcylindrical base, 800-1300 /a wide or more, 150-200 ju, thick in the 

 center, tapered to the thin (30-40 fi) edges, the usually rounded apices in 

 youth with a distinct apical cell, in age becoming attenuated and cylin- 

 drical and often more or less contorted ; older blades becoming closely 

 pinnately branched near the extremities, some of these branches ligulate, 

 others subcylindrical or cylindrical, readily deciduous and apparently 

 serving as a vegetative means of reproduction; internal structure con- 



