NO. 10 DAWSON : MARINE ALGAE, GULF OF CALIFORNIA 275 



tached to the shell as well, including a small tuft of Ulva. This character 

 and its loosely attached habit with tendency to ascend and form free parts 

 make this plant distinct from any others known. 



Genus LITHOLEPIS Foslie 



Litholepis sonorensis sp. nov. 



Plate 63, Fig. 1 



Frondes monostromaticae, superpositae usque ad 4-stratosae, crustam continu- 

 am, arete ad substratum adhaerentem ad superficies totas concharum raagnaruni 

 duratarum tegentem, obscure cinereo-albae formante; cellulis magnitudine varia- 

 bilis, plerumque recto elongatis, 13-25 [a altis; conceptaculis tetrasporangiiferis 

 humilibus, conicis, poro singulo, circa 400 [i in diam. externe, 175 [x, altis, cavitate 

 interna 300 n in diam., disco piano, parietibus supernis crassioribus (circa 3- 

 stratosis) porum circumferentibus; tetrasporangiis circa 50 \i altis, discum circum- 

 vallentibus. 



Thalli monostromatic, growing superposed over one another, to 2-4 

 layers, forming a continuous, closely adherent crust over all the surfaces 

 of large, weathered shells, dull gray-white in color ; cells variable in size, 

 mostly elongated slightly vertically, 13-25 /a high; tetrasporangial con- 

 ceptacles low, conical, with a single pore, about 400 /x external diam., 175 

 ju, high; internal cavity 300 jx diam., with a flat disk, the upper wall 

 thickest (about 3 layers) around pore; tetrasporangia about 50 fx long, 

 arising from the periphery of the disk. 



Type: D. 592x, growing on a large weathered shell, dredged in 

 San Lorenzo Channel, Espiritu Santo Island, Feb. 14, 1940. Herb. AHF 

 no. 27. 



No species of this genus has been described from the Pacific American 

 coasts. The large size of the thin, superposed crusts of this species, com- 

 pletely covering extensive surfaces, seems to be a character distinguishing 

 it from the several known in Atlantic waters. More complete collections 

 will be necessary, however, to verify this. The described species have not 

 been illustrated, and it is difficult to compare habit characters from the 

 existing descriptions. 



Genus GORALLINA (Tournef.) Lamouroux 

 Corallina pilulifera Post. & Rupr. 



Postels & Ruprecht, 1840, p. 20, tab. XL, fig. 101 ; Yendo, 1902a, p. 30, 

 pi. Ill, figs. 14-16, pi. VII, figs. 14-16. 

 Our plants correspond most closely to form sororia of Ruprecht. It is 

 a common middle and lower littoral species in the rock-cover vegetation 

 of the northern Gulf and is abundant in many tidal pools. 



