538 BULLETIN OF THE BUREAU OF FISHERIES. 



eef . Frond horizontally expanded forming small, more or less definite, disk-shaped spots 



on the substratum qf. 



gf. Frond thin, consisting of a single uniform layer; larger cells present among ordi- 

 nary cells; conceptacles small MELOBESIA (p. 523). 



ggf . Frond fairly thick, differentiated into a thin basal layer and a thicker upper 



one ; cells of fairly uniform size ; conceptacles large DERMATOLITHON (p. 524). 



eetf . Frond forming indefinite expansions over the substratum h'. 



h'. Tetrasporangial conceptacles opening by a separate pore for each sporangium 



LlTHOTHAMNIUM (p. 524). 



hh'. Tetrasporangial conceptacle opening by a single apical pore LITHOPHYU.UM (p. 525). 



