114 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



medulla multizonal, of flexuous, interlacing filaments; genicula only 

 slightly visible between intergenicula, unizonal, 300-400 /x long, of 

 straight filaments; tetrasporangial conceptacles domoid, up to 1 mm. in 

 diameter, borne irregularly on flattened faces of intergenicula, on the 

 lateral margins of the wings and in part on the upper margins of the 

 wings; tetrasporangia 150-190 /a long, oblong; sexual plants not identi- 

 fied in the Mexican material. 



Type: Holotype not designated. Syntypes are represented by tetra- 

 sporic specimens on sheet 545724, and antheridial specimens on sheet 

 545721 in the Herbarium of the University of California, Berkeley. 



Type locality : Two syntype localities are indicated : Pacific 

 Grove and Pebble Beach, both in Monterey County, California. 



Mexican distribution: Pacific Baja Calif. — D. 4256, at depth 

 of 18 meters, Islas hos Coronados, June; Cooper 769, Punta Santo 

 Tomas, March; D. 8836, Punta Baja, Jan.; D. 10583, drift, Punta 

 Norte, Isla Cedros, Oct.; Schmitt 287A-34, at depth of 17-24 meters, 

 South Bay, Isla Cedros, March. 



This species is characteristic of the cool waters of central California. 

 In Mexico its intertidal occurrence is apparently limited to the northern 

 localities of maximum upwelling intensity. The two dredged collections 

 indicate that it may be expected to occur more widely in the sublittoral. 



Key to the Mexican Species of Jania 



1. Segments markedly compressed throughout 



J. tenella var. zacae 



1. Segments normally all cylindrical, rarely a little compressed 



below 2 



2. Thallus with frequent alternate or opposite pinnate branches 

 in addition to the primary dichotomous branching 



J. subpinnata 



2. Thallus strictly dichotomously branched .... 3 



3. Thalli decussate-dichotomously branched with relatively wide 

 angles mostly over 45° 4 



3. Thalli not markedly decussately branched ; angles rather nar- 

 row, mostly 45° or less (sometimes prominently decussately 

 branched in /. longiarthra, but angles very narrow ... 5 

 4. Segments 60-100 /* in diameter . . . J. capillacea 

 4. Segments mostly 120-170 /a in diameter .... 

 /. decussato-dichotoma 



