10 M. FOSLIE. [1902 

Melobesia (Heteroderma) marginata Setch. et Fosl. mscr. 
Thallus forming orbicular crusts, at length extended patches on 
other algae, 50—100 p thick; conceptacles of sporangia crowded, 
convex or subconical, 150—200 yp in diameter. 
The plant at first forms small orbicular or sometimes rather 
irregular, purplish crusts on other algae. These crusts by and by 
anastomose and at length form extended patches almost covering 
certain parts of the frond of Gymnogongrus linearis or Lawrencia 
pinnatifida. Steril specimens probably belonging to the same spe- 
cies have also been met with on Odonthala dentata. The crust 
is 50—100 p thick and composed of at least up to 9 layer of 
cells. The basal cells are almost square or, more frequently, verti- 
cally elongated, up to 12 » long and 5—8 p» broad. The upper cells 
on a section are square or somewhat rounded, 6—8 } in diameter, 
or vertically elongated, up to 10 » long, occasionally forming short 
rows with the longest diameter in horizontal direction. The cortical 
cells are smaller. The cellwalls are frequently rather thick. 
The conceptacles of sporangia are densely crowded almost 
over the whole frond, often so densely that the roofs partly ana- 
stomose, sometimes however forming small groups as in Melobesia 
Cymodoceae. They are convex but little prominent, or subconical, 
.150—200 p in diameter seen from above. The sporangia are four- 
parted, 50-60 p long and 25—30 yp broad. 
Dried specimens of this species with emptied conceptacles some- 
what resemble Lithothamnion corticiforme in habit. On the other 
hand the species approaches Melob. zostericola and M. Cymodoceae. 
Occurrence. Pacific coast of North America: Bodega Bay, 
California, on Gymnogongrus and Laurencia; and Whidbey Island, 
Wash., on Laurencia pinnatifida, and in the same locality on 
Odonthalia (steril), Setchell and Gardner, Algae of Puget 
Sound No. 269, 270. 
Melobesia (Eumelobesia) rugulosa Setch. et Fosl. mscr. 
Thallus monostromatic exsept in the neighbourhood of the 
conceptacles, without cortical cells. Conceptacles of sporangia © 
subconical, 120—150 yp in diameter. 
4 
—”? CC “il 
