336 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3 



branches; polysiphonous main axis with four pericentral cells, 50-70 /x 

 diam., the pericentral about 2 diam. long; lateral branches 400-700 /x 

 long, 25-40 IX diam. at base, arranged one to a segment in a I/4 spiral, 

 simple or with 2-3 limbs from near the base, subulate, usually somewhat 

 cui-ved upward, with a sharp-pointed terminal cell ; tetrasporangia borne 

 in a single spiral row of 8-15, one per segment, in slightly swollen por- 

 tions of main axes a short distance below apices, about 50 ju, diam. when 

 mature. 



Type: D, 381d, growing on a small hydroid, dredged in 22 meters, 

 Tepoca Bay, Feb. 4, 1940. Herb. AHF no. 63. 



Genus BOSTRYGHIA Montagne 

 Bostrychia radicans Mont. 

 Plate 49, Figs. 3, 4 



Montagne, Cryp. Guy., 1842, p. 419; Post. 1936, p. 13. Bostrychia rivtt- 

 laris Harvey, 1852-1858, p. 57, pi. XIV D. 

 An ample collection of this species was made by Drouet & Richards 

 on the Sonora coast near Guaymas and may be expected widely on sub- 

 merged wood or Mangrove roots in the bays and lagoons of the more 

 southern regions of the Gulf. It was distinguished as B. rivularis by 

 Collins and Hervey from other known American Bostrychia species 

 (1917) by its ecorticate main axis. Post includes R. rivularis under B. 

 radicans, to which she attributes very wide world distribution. The pres- 

 ent specimens, however, are the first Pacific North American examples. 



