MARINE AI<GJE OF BEAUFORT, N. C. 525 



cystocarps borne in more or less conical, superficial, or slightly sunken conceptacles, 

 each conceptacle opening by a single apical pore, carpospores arising from the periphery 

 of the fusion cell, the central part of the fusion cell bearing a few elongated, evanescent 

 paraphyses; antheridia and cystocarps apparently borne on different plants. 



About 80 species, widely distributed, mostly in warm seas. 



This genus has been variously characterized by different authors and is still not well 

 understood. It is distinguished from Lithophyllum chiefly by the fact that each spo- 

 rangium communicates with the exterior by a separate pore, so that the surface of a 

 mature tetrasporangial conceptacle, when viewed with a lens, looks like a miniature 

 pepperbox. The species are exceedingly difficult and can be determined only by those 

 who are familiar with them or by comparison with authentic specimens. In some cases 

 the same species seems to show different forms on different substrata. 



Lithothamnium sejunctum Foslie (?). 



Lithothamnion sejunctum, Fosile, 1906, p. 3. 



Thallus disk shaped, almost spherical, later confluent and irregular, rather thick, forming masses 

 incrusting stones, etc., strongly calcined and closely attached to the substratum, showing slight, con- 

 centric zonation; composed of two distinct strata, the lower (hypothallium) composed of several layers 

 of cells about n to 18 by 5 to 9 mic., the upper (perithallium) composed of several layers of cells, these 

 cells squarish, 5 to 7 mic. in diameter or slightly vertically elongated, sometimes slightly horizontally 

 elongated; tetrasporangial conceptacles embedded, hemispherical, 160 to 260 mic. in diameter, bearing 

 about 40 pores; cystocarpic conceptacles hemisphericalconical, 200 to 300 mic. in diameter. 



West Indies. 



Incrusting coral rock dredged from coral reef offshore, Beaufort, N. C., May, 1907 (?). 



To this species is referred, with some doubt, an antheridial plant incrusting a part of one piece of 

 coral rock, but the determination can not be made with assurance, since no authentic specimen has been 

 available for comparison. It does not seem to belong to any other described species, and has not seemed 

 to deserve description as a new species. It is probable that much of the coral rock dredged from the reef 

 bears this plant, but only one piece has been available for examination. On this piece the plant here 

 referred to occurs alongside Lithophyllum intermedium. From the latter species it is distinguished with 

 difficulty. As found here, it has a slightly rougher, less glistening surface than the Lithophyllum. In 

 section the two strata are more sharply denned than in the latter form. This species has not been 

 recorded elsewhere outside of the West Indies. 



Genus 4. Lithophyllum Philippi. 



Lithophyllum, Philippi, 1837, p. 387. 



Thallus forming a more or less irregular incrusting mass, more or less closely attached 

 to the substratum, margin free or loosely attached, undivided or variously lobed, some- 

 times bearing irregular proliferations, strongly incrusted with lime, composed of two 

 strata, cells rather regularly arranged, radiating toward the periphery, those in the upper 

 perithallium smaller than in the lower hypothallium; tetrasporangia borne in sunken 

 or somewhat prominent conceptacles, these conceptacles hemispherical-conical, at first 

 convex, then losing more or less of the cortex, becoming somewhat depressed, the entire 

 conceptacle communicating with the exterior by a single central pore; cystocarps borne 

 in sunken or somewhat prominent, convex conceptacles, carpospores accompanied by a 

 central mass of short paraphyses. 



About 50 species, mostly in warm seas. 



This genus has been variously characterized by different authors and is still not 

 well understood. It is distinguished from Lithothamnium chiefly by the fact that the 

 entire tetrasporangial conceptacle communicates with the exterior by a single apical 



