NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 67 



Mexican distribution: D. 8504, 8383, Isla Guadalupe, Dec. 

 (tetrasporic). Both of these collections seem to be identical with material 

 of this species collected on Santa Catalina Island, California (Dawson 

 1949a, p. 24), It remains the only outstandingly polystichous Gelidium 

 thus far known from the Pacific Coast. 



Gelidium decompositum Setchell & Gardner 



Setchell & Gardner, 1924, p. 743, pi. 71 ; Dawson, 1944, p. 260. 



Thalli 6-9 cm. high, attached to crustose corallines on rocks by a 

 few loose, creeping stolons with more or less penetrating branches, con- 

 sisting above of one or a few, much-branched erect fronds which are 

 flattened throughout; central axis 0.6-0.8 mm. (or up to 1.5 mm.) wide, 

 divided irregularly some distance from the base into several primary 

 branches, these in turn densely 2-3 times irregularly, alternately pinnate- 

 ly branched, each order successively more slender but flattened ; pinnae 

 of each different order variable in length, nearly perpendicular to the 

 axis of origin, those of the ultimate and subultimate orders often densely 

 matted together; rhizoidal filaments absent in terminal and subterminal 

 ramuli, scattered through the medulla of primary axes; reproduction 

 unknown. 



Type: Holotype is Johnston 23, June 1921, No. 1344 in the Her- 

 barium of the California Academy of Sciences, San Francisco, California.. 



Type locality: Bahia San Francisquito, Baja California, Mexico. 



Mexican distribution: Gulf of Calif. — D. 1021, Isla Partida, 

 Feb.; D. 1038, Isla Raza, Feb. 



This remarkable plant which resembles the densely branched form 

 of Pterocladia pyramidale in gross aspect, is known only from a very 

 small region in the northwestern Gulf of California. Although specimens 

 have been taken both in February' and in June, reproductive material has 

 not yet come to light. The structure of the thallus in transection seems 

 to be that of Gelidimn, though one should recognize the possibility that 

 the plant may prove to be a Pterocladia. 



Gelidium coronadense sp. nov. 

 Plate 4, fig. 6 ; Plate 22, figs. 2-3 



Thallis dense rosulatis, 3-4 cm. altis ; partibus erectis 3 ordinum 

 ramorum planorum 150-210 /a crassis, dense congestorum, pinnatorum, 

 alternatorum oppositorumve, cuiusque ordinis 900-200 ^ continenter 

 angustioris; ramis deciduis a parte inferiore caulis; filamentis rhizoideis 



