14 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



often more or less constricted, the cells becoming quaternately and then 

 more extensively radially divided, ultimately irregularly divided; thalli 

 dioecious; antheridia formed from repeated divisions of the vegetative 

 cells, yellowish ; spermatia 3-4 /* in diameter ; carpogonia formed by im- 

 mediate transformation of vegetative cells. 



Type: Holotype not designated and the whereabouts of Dillwyn's 

 original material collected by W. W. Young unknown to the writer. It 

 is not among the Dillwyn types at the Linnaean Society, London. 



Type locality: On limestone rocks near high water mark, vicin- 

 ity of Dunraven Castle, Glamorganshire, Wales. 



Mexican distribution: Pacific Baja Calif. — D. 97, Cabo Col- 

 nett, Jan.; D. 151-45, near Punta Descanso, Apr. (sexual) ; D. 8696, 

 Punta Baja, Jan.; D. 1480, Punta Santa Rosalia, Apr. (sexual); D. 

 7270, Bahia Santa Maria, Apr. (sexual). Gulf of Calif.— D. 981, Isla 

 Partida, Feb. (sexual). 



The Isla Partida and Punta Santa Rosalia specimens represent a 

 variant in which the cells of the lower parts of the filaments are com- 

 monly longer than broad and less than 8 /x in diameter. 



Porphyra Hollenbergii sp. nov. 

 Plate 13, fig. 1 



Porphyra perforata f. segregata Hus., as interpreted by Dawson, 

 1944, p. 253. 



Thallis saxicolis, ex aliquot laminis monostromaticis, valde crispis, 

 lanciolatis vel lineolanciolatis, dioeciis; areis fertilibus marginalibus, 

 continuis ; 64 spermatiis in f asciculis singulis ; 8 carposporeis in fasciculis 

 singulis. 



Thallis saxicolous, membranous, 6-15 cm. high, pale rose tending 

 toward greenish in color, consisting of several much-ruffled, lanceolate 

 or linear-lanceolate, more or less lacerate blades arising from a common 

 basal, membranous area attached by a very small disc; blades 1.0-3.5 cm. 

 wide, monostromatic, 45-55 /x thick, of cells to 20 /x, in greatest diameter 

 at the surface, to 23 /x deep ; plants dioecious ; spermatia in packets of 64 

 forming a continuous yellowish margin on either side of the blade; 

 carpospores in packets of 8, unmixed with vegetative cells, forming a 

 continuous, slightly darker zone along either margin of the blade. 



Type: Holotype is Dawson 539-40, Feb. 12, 1940, on sheet 50462 

 in HAHF. 



Type locality: Upper littoral rocks, Bahia Agua Verde, Baja 

 California (Gulf coast), Mexico. 



