524 



BULLETIN OF THE BUREAU OF FISHERIES. 



Fairly abundant on various algse dredged from the coral reef offshore, Beaufort, N. C., August, 1914. 

 As found in Europe, the form grades over into the species, but in this region it seems, while approach- 

 ing the habit of the species, to remain distinct. 



This form has not previously been reported from North America. 



Another species, M. lejolisii Rosanoff , a more northern species than the above, may 

 be found within our range, but has not been observed by the author. This is distin- 

 guished from the present species by the absence of " heterocysts " in the frond and the 

 presence of conspicuous cilia bordering the openings of the conceptacles. 



The only other species recorded for this region that is likely to be mistaken for the 

 above is Dermatolithon pustulatum (Lamour.) Foslie. The latter is distinguished by its 

 thicker frond and larger, more conspicuous conceptacles. 

 f Genus 2. Dermatolithon Foslie. 



. Dermatolithon, Foslie, 1900, p. 21. 



Thallus forming a small, flattened disk, attached to the substratum by the entire 

 under surface, strongly incrusted with lime, composed of two distinct strata, the lower, a 

 thin hypothallium, usually consisting of a single layer of elongated cells, and the upper, a 

 thicker perithallium, consisting of several layers of cells; tetraspongia borne in flask- 

 shaped conceptacles somewhat immersed in locally thickened portions, each concep- 

 tacle opening to the exterior by an apical pore; sporangia borne only on the sides of the 

 conceptacle, the middle being occupied by paraphyses; cystocarps borne in flask- 

 shaped, somewhat immersed conceptacles opening by apical pores, carpospores accom- 

 panied by paraphyses. 



About 10 species, generally distributed, especially in warm seas. 



Dermatolithon pustulatum (Lamouroux) Foslie. 



Melobesia pustulata, Lamouroux, 1816, p. 315, pi. 12, f. c, B. 

 Melobesia Pustulata, Farlow, 1882, p. 181. 

 Dermatolithon pustulatum, Foslie, 1900. p. 21. 

 Dermatolithon pustulatum, De Toni, 1905, p. 1771- 

 P. B.-A. No. 300 (Melobesia farinosa). 



Frond forming rather small, rather thick, flat, rather rounded more or less confluent disks, 2 to 10 

 mm. in diameter, surface not farinaceous, composed of two differentiated strata, hypothallium consisting 

 of vertically elongate cells, perithallium consisting of rather square cells, "heterocysts " lacking; concep- 

 tacles large, conspicuous, 0.3 to 0.5 mm. in diameter, scattered over the thallus, opening by single, 

 central pores, not bordered by cilia. 



Widely distributed. 



Very abundant on Zostera marina and often on other algae throughout the harbor and on Bogue 

 Beach, Beaufort, N. C. 



This species often occurs in pure growths almost covering the leaves of Zostera. It is distinguished 

 from Melobesia farinosa, the only other species observed here with which it is likely to be confused, by 

 its thicker frond, its larger, more conspicuous conceptacles, and the absence of "heterocysts." 



Genus 3. Lithothamnium Philippi. 

 Lithothamnium, Philippi, 1837, p. 387. 



Thallus forming a more or less irregular incrusting mass, attached to the substratum 

 by the entire under surface, frequently giving off from this base more or less numerous 

 wartlike, stemlike, or corallike outgrowths of various, frequently irregular, shapes, strongly 

 incrusted with lime, composed of two strata, cells more or less regularly arranged ; tetra- 

 sporangia borne in superficial or somewhat sunken conceptacles, each sporangium 

 opening to the exterior by a separate pore, sporangia zonately divided; antheridia and 



