NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 85 



Type: Holotype is Dawson 237-40, Jan. 28, 1940, on sheet 20, in- 

 cluding slides 016-019 in HAHF. 



Type locality: In beach drift on north shore of Puerto Refugio, 

 Isla Angel de la Guarda, Baja California, Mexico. 



A collection from Bahia San Carlos, Sonora (D. 1882, May, 1946) 

 has the vegetative appearance and structure of this plant, but is sterile. 



The peculiar large monospore-like bodies of this plant, unknown 

 elsewhere in the Gelidiales, are not understood and require investigation 

 of more ample material. 



Gelidiopsis tenuis Setchell & Gardner 



Setchell & Gardner, 1924, p. 749, pi. 22, fig. 2; Dawson, 1944, p. 

 264, pi. 70, Hg. 1 ; Dawson, 1949, p. 246. 



Thalli to 6 cm. high, consisting of many loose, remotely branched, 

 terete or compressed branches arising from a spreading tangle of loose 

 stolons attached to corallines or debris by small discs ; erect parts openly 

 and irregularly alternately, suboppositely or subdichotomously branched 

 at intervals of 2-10 mm.; segments 250-400 /a in diameter, the terminal 

 ones sometimes 2 cm. long ; apices rounded, without an apical cell ; struc- 

 ture consisting of a medullary core of cells 8-9 ju. in diameter and 12-15 

 diameters long surrounded by shorter and larger medullary cells to 30 

 fj. in diameter merging into a 2-3 layered cortex whose outermost cells are 

 about 8 fjiin greatest diameter ; reproduction unknown. 



Type: Holotype is Marchant 104 in the Herbarium of the Cali- 

 fornia Academy of Sciences, San Francisco, California. An isotype is on 

 sheet 21, including slides 020 and 1352, in HAHF. 



Type locality: Santa Rosalia, Gulf coast of Baja California, 

 Mexico. 



Mexican distribution: Gulf of Calif. — D. 648 (Feb.), D. 3581 

 (Nov.), near Guaymas; D. 475b-40, dredged from 30-36 m., Ensenada 

 de San Francisco, Feb. ; D. 543-40, 533b-40, Bahia Agua Verde, Feb. ; 

 D. 3105, Cabo Pulmo, Nov.; D. 3271, Punta Palmilla, Nov.; Howell 

 605 (Herb. Calif. Acad. Sci.), dredged from 40 m. off San Jose del 

 Cabo. Sinaloa—D. 3686, 3636, Mazatlan, Dec. Nayarit—D. 3692, 

 Mira Mar., Dec. Revillagigedo Archip. — Howell 514 (Herb. Calif. 

 Acad. Sci.), Isla Clarion, 



This species is much like Gelidiopsis variabilis in habit and in struc- 

 ture, but is smaller in all dimensions. A reexamination of the type 

 material shows that the segments are not .5-.8 mm. in diameter as ori- 

 ginally described, but are 250-400 yx in diameter, only basal parts reach- 

 ing 500 {x. 



