120 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



ous by two horn-like propections from the shoulders, these usually 

 developing into branchlets of 1 -several segments which in turn end in 

 conceptacles and repeat, a conceptacle, thus, often supporting 1-4 suc- 

 cessive forkings in which case the branching becomes more divergent 

 than in the sterile parts; antheridial plants with narrow branch-angles; 

 antheridial conceptacles elongate-ellipsoidal, 240-279 fi in diameter, 450- 

 600 fi long, apically rather acute, strictly terminal and non-antennifer- 

 ous; antheridia fusiform, about 5 by 2 /a in dimensions; cystocarpic plants 

 not seen. 



Type: Holotype is Taylor 34-569, Mar. 2, 1934, in box 3631 in 

 HAHF. 



Type locality : Bahia Petatlan, Guerrero, Mexico. 



Mexican distribution: Sinaloa — D. 3617, 3649, Mazatlan, 

 Dec. Nayarit — D. 3705, Mira Mar, Dec. Jalisco — D. 3752, Barra de 

 Navidad, Dec. Guerrero — Hubbs 46-234, Acapulco, Sept. Oaxaca — 

 Taylor 34-553, Bahia Tangola-Tangola, Feb.; D. 3827, 3785, Salina 

 Cruz, Jan. 



The successive compounding of the tetrasporic conceptacular 

 branches is distinctive in this densely tufted little plant which appears to 

 range along the whole of the tropical mainland coast of Mexico. The 

 antheridial plants are rare compared to the abundant, fertile, asexual 

 individuals. 



Jania tenella Kiitzing var. tenella 

 Plate 9, fig. 3 



Kiitzing, 1858, Tab. Phyc. 8: p. 41, pi. 85, fig. 2; Dawson, 1949a, 

 p. 25. Jania rubens (L.) Lamx., as interpreted by Setchell & Gardner, 

 1930, p. 179. Corallina ungulata Yendo, as interpreted by Collins, 

 Holden & Setchell in Phyc. Bor. Am. No. 1050. 



Thalli usually epiphytic, but sometimes saxicolous, forming soft, 

 dense tufts covering considerable parts of the host, 1-2 cm. high, con- 

 sisting of many congestedly branched erect parts from an inconspicuous 

 disc, cylindrical throughout, or sometimes the lower segments somewhat 

 compressed; branching strictly dichotomous, often subcorymbose, es- 

 sentially in one plane, or sometimes with an obscure tendency toward 

 decussate arrangement, the angles rather narrow, the internodes pro- 

 gressively shorter toward upper parts of plants; intergenicula 60-120 

 /A in diameter, (2.5) 3 to 5 (6) diameters long; apices subulate, or some- 

 times ungulate in growth; tetrasporangial conceptacles about 250 ii in 



