158 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



zonal, (160) 180-200 (240) /x long; intergenicular medullary filaments 

 essentially straight ; reproductive conceptacles irregularly placed on geni- 

 cular faces, usually on either side of axis, tetrasporangial ones domoid, 

 400-600 IX in diameter, 2-4 per segment, antheridial ones domoid- conical, 

 slightly rostrate, 350-500 fi in diameter, 2-6 per segment. 



Type: Holotype is Silva 4880, Feb. 26, 1949, in the Herbarium 

 of the University of California, Berkeley. Isotype is in HAHF. 



Type locality: Lower littoral rocks. South Island, Los Corona- 

 dos, Baja California, Mexico. 



Additional material: California — Silva 4309, Johnsons Land- 

 ing, Santa Catalina Island, Feb. ; Silva 2498, Catalina Harbor, Santa 

 Catalina Island, Feb.; Silva 4412, Santa Barbara Island, Feb.; Silva 

 2691, Willows Anchorage, Santa Cruz Island, Jan.; Silva 1500, West 

 Anacapa Island, Mar. (a proliferous, rather thin form) ; Silva 1518, 

 Prisoners Harbor, Santa Cruz Island, Mar.; Silva 1521, Wilson Cove, 

 San Clemente Island, Aug. Pacific Baja Calif. — D. 10406, Punta San 

 Eugenio, Nov. 



The gross outline of this species is so variable that one is inclined 

 at first to recognize two species. Some of the plants are so regularly 

 and compactly corymbose as to suggest Bossea corymbifera Manza, while 

 others are not at all corymbose and have elongated ultimate branches of 

 unequal length. The distinctive shape of the usually rather thick, sagit- 

 tate intergenicula, the characteristic percurrent axes and pinnate branch- 

 ing, and the cylindrical, basal stipitate parts seem clearly to ally all of 

 these collections and to distinguish them from other species of this coast. 



The Punta San Eugenio specimens are somewhat less coarse than the 

 others. 



That the number of conceptacles may be extremely variable is indi- 

 cated by several specimens under Silva 4309 in which seven tetrasporfc 

 conceptacles or twelve carposporic ones may occur on one face of a 

 segment. 



Bossea cooperi Dawson et Silva sp. nov. 

 Plate 8, fig. 7 ; Plate 24, fig. 2 



Thallis 4-9 cm. altis, dumosis, abundanter ramificatis intervallis 3-6 

 intergeniculorum, ramificatione dichotoma pinnataque ubique plus min- 

 usve irregulariter mixta, at ramificatione pinnata, alternata oppositeve 

 praevalente; intergeniculis sagittatis, paulo latioribus quam longioribus, 

 1.5-2.5 mm. latis, 1.2-2.0 mm. longis, crassioribus, lobis brevibus, sub- 

 acutis, costa indistincta. 



