478 BULLETIN OF THE BUREAU OF FISHERIES. 



Antheridia and cystocarps have been described for one species of Actinococcus, but 

 this observation seems founded on insufficient evidence. 



Actinococcus aggregatus Schmitz. 



Actinococcus aggregatus, Schmicz, 1893, p. 385, pi. 7, f- 8. 

 Actinococcus aggregatus. De Toni, 1897. P- 259- 

 P. B.-A. No. 786. 



Parasitic on Gymnogongrus griffithsiae, the vegetative portion occurring as fine filaments between 

 the cells of the host ; fruit appearing as a protuberant pad on the surface of the host , minute , about i mm . 

 wide, rounded, flattened convex, single or several approximate; tetrasporangia cruciately divided, 

 often imperfectly septate. 



North Atlantic and Pacific; Mediterranean Sea. 



On about one-fourth of the specimens of Gymnogongrus griffithsiae, Fort Macon jetties, Beaufort N. C. 



Family 2. RHODOPHYLLIDACE^E Schmitz. 



Frond terte, flattened, or foliaceous, dichotomously or laterally branched; structure 

 cellular or cellular-filamentous, seldom filamentous; tetrasporangia usually scattered 

 over the thallus surface, sometimes collected into numerous son, sunk in the outer 

 cortex, which is often thickened to form nematheciumlike structures, nearly always 

 zonately divided ; antheridia usually in patches more or less widely distributed over the 

 surface; carpogonia numerous on the fertile portions of the thallus, sometimes distant 

 from the auxiliary cells and, after fertilization, fusing with one of these by a filament; 

 auxiliary cells usually less numerous than the carpogonia, sometimes not formed until after 

 fertilization; cystocarps scattered over the thallus, often situated at the edges, immersed 

 or more or less prominent, usually provided with a conspicuous pore; gonimoblast 

 suspended from an upper wall of the cystocarpic cavity, divided into several lobes 

 radiating in all directions, forming spores in the apical cells of the filaments and some- 

 times in the subapical ones also. 



About no species, all marine, in all parts of the world. 



KEY TO GENERA. 



a. Auxiliary cell forms on a protuberance bearing filamentous tufts, which radiate in every 



direction and branch outward fasciculately b. 



b. Frond terete, radially branched, subtubular above, of cellular-filamentous structure 



." i . Agardhiella (p. 478). 



bb. Frond foliaceous, usually pinnately or furcately divided, with numerous warts or 



papillae on the surface and margins 2. Meristotheca (p. 479). 



aa. Auxiliary cell extends a thick projection into the cystocarpic cavity and bears at its apex 



numerous tufts of filaments c. 



c. Frond terete or slightly flattened, laxly tubular, sometimes caulescent and solid below 



3. Rhabdonia (p. 480). 



cc. Frond terete or flattened, structure dense, rigid, furnished with short, acute or obtuse, 



simple or branched papillae 4. Eucheuma (p. 481). 



Genus i. Agardhiella Schmitz. 



Agardhiella, Schmitz, 1889, p. 441 (7). 



Frond terete, branched on all sides, subtubular and rather lax above, structure 

 cellular-filamentous, medullary filaments reticulately anastomosing, more or less lax, 

 cortex large celled within, very small celled without; tetrasporangia scattered over the 

 surface, zonately divided; auxiliary cells not united with the carpogonia, scattered 

 throughout the frond; cystocarps scattered through the frond, entirely immersed or 



