228 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3 



Family Dictyotaceae 



Genus DIGTYOTA Lamouroux 

 Dictyota crenulata J. Ag. 



J. Agardh, 1847, p. 7 ; Setch. & Gard., 1924, p. 730, pi. 18, figs. 50, 51. 



A collection taken from beach drift at San Jose del Cabo, D. 629x, 

 February, is identical with that previously reported from the Gulf, name- 

 ly. Brand, 24, from La Paz. Taylor ( 1939, p. 8) has reported it from off 

 Punta Gorda in 12-20 meters, Waldo Schmitt, 7, July, 1938. 



The author's specimens average 10 cm. high, are finely but conspicu- 

 ously denticulate and richly proliferous with sporelings as mentioned by 

 Setchell and Gardner (loc. cit.). 



Dictyota hesperia S. & G. 



Setch. & Gard., 1924, p. 731, pi. 18, figs. 52, 53. 



D. 713, 718, middle littoral rocks. Turner's Island, July. 



The present specimens compare well with the type from Tortuga 

 Island, J. 32 (AHF no. 71), and with the cotype from San Marcos 

 Island, J. 5, both collected in June. The species seems to be a summer an- 

 nual, since it was not found at the Turner's Island station in January. Its 

 smaller size, 3-5 cm., and narrower segments, 1-1.5 mm., serve to distin- 

 guish it from the much more abundant Dictyota Johnstonii of the same 

 habitat. 



Dictyota Johnstonii S. & G. 



Setch. & Gard., 1924, p. 730, pi. 18, figs. 54-56, pi. 39. 



J. 4, lower littoral rocks, San Marcos Island, June; J. 81 (AHF no. 

 70), Isla Partida, July; D. 95, rocky reef, Turner's Island, January, D. 

 740, July; D. 659, middle littoral rocks north of Kino, July; D. 686, 

 cobblestone beach, south shore of Tiburon Island, July; D. 155, dredged 

 in 4-32 meters off south shore of Tiburon Island, Jan. 



The winter and summer collections at Tiburon Island in 1940 have 

 revealed much concerning the seasonal development of this species. Jan- 

 uary collections on the reef at Turner's Island and off the shore of Tib- 

 uron Island yielded a few plants, mostly very young. At that season indi- 

 vidual plants were only occasional and formed no conspicuous colonies. 

 The surface temperature in January was 15.5-16° C. In July, when the 

 first low-tide collections were made on the shore of Tiburon Island, the 



