202 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3 



dentate. Our specimens are generally shorter and somewhat broader than 

 the type, and frequently have less conspicuous undulation of the margins. 



Ulva rigida Ag. 



C. Agardh, 1822, p. 410; Setch. & Gard., 1920, p. 269; 1924, p. 717. 



On upper littoral rocks at Turner's Island an abundance of this small, 

 crisp, tufted species was found. It was noted in the upper littoral at other 

 stations in the northern part of the Gulf, but apparently collecting of it 

 was neglected. This species may be distinguished from young plants of 

 Ulva lactuca, which often resemble it, by the thicker fronds and the 

 vertical elongation of cells in cross section. The small, ruffled blades do 

 not expand broadly as in U. lactuca. 



D. 114, Turner's Island, Jan. 



Ulva lactuca L. 



Linnaeus, 1753, p. 1163; Setch. & Gard., 1920, p. 265; 1924, p. 717. 



Twenty-one collections of this cosmopolitan species are present from 

 various localities and habitats in the Gulf, from La Paz to Punta Pefiasco. 

 It is distinguished from the other three Gulf species by its broadly ex- 

 panded fronds and quadrate cells in cross section. 



Genus ENTEROMORPHA Link 



For the most part, Setchell and Gardner, 1924, can be followed in the 

 identification of the Gulf species or forms of Enteromorpha. Our speci- 

 mens of E. acanthophora correspond closely with the material they ex- 

 amined. This species is quite distinct in habit from any others from the 

 region. 



EnteroTnorpha Marchaniae, on the other hand, should certainly be 

 considered nothing more than a form of E. intestinalis. I cannot confirm 

 the distinctions made in the original description. Since Enteromorpha 

 "species" are so often merely form names, it is difficult to justify the ad- 

 dition of more names for minor shape differences in these variable and 

 undoubtedly much hybridized plants. 



Enteromorpha prolifera in the Gulf is usually much finer in habit 

 than E. compressa and shows more fine proliferations as well as cells in 

 more or less longitudinal series. It seems best here to follow Collins in 

 listing E. tubiilosa as a synonym or variety of E. prolifera. The Gulf ma- 



