,526 BULLETIN OP THE BUREAU O'F FISHERIES. 



pore; in most cases, at least, the cells also are arranged in more regular layers than in 

 Lithothamnium. The species are exceedingly difficult and can be determined only 

 by those who are familiar with them or by comparison with authentic specimens. 

 Lithophyllum intermedium Foslie. 



Lithophyllum intermedium, Foslie, 1906, p. 23. 



Thallus disk shaped, almost spherical, later irregular, up to about 3 mm. thick, forming masses 

 incrusting stones, etc., more or less closely attached by the under surface, bowl shaped or irregular, 

 edges scalloped or irregular; showing two distinct strata, the lower (hypothallium) weakly or strongly 

 developed, composed of several or many layers of cells n to 25 by 7 to n mic., the upper (perithallium) 

 composed of several layers of cells almost always vertically elongated, 9 to 22 (usually 9 to 18) mic. 

 long and 7 to n mic. broad; tetrasporangiial conceptacles somewhat convex, not sharply defined, 150 

 to 250 or up to 300 mic. diameter. 



Florida; West Indies. 



Incrusting coral rock dredged from coral reef offshore, Beaufort, N. C., May, 1907, one small sterile 

 plant on base of Sargassum filipendula dredged from coral reef, July, 1915. 



This species will not be mistaken for any other found in this region except Lithothamnium 

 sejunctum (?). From the latter it is distinguished with difficulty. As found here it has a slightly 

 smoother, more glistening surface, and in section the two strata are less sharply defined than in the 

 Lithothamnium. It is probable that much of the coral rock dredge^ from the reef bears this plant, 

 but only one piece has been available for examination. On this it "occurs alongside Lithothamnium 

 sejunctum (?) , and bears numerous tetrasporangial conceptacles. This is the northern known limit for 

 the species and the genus. 



Genus 5. Amphiroa Lamouroux. 



Amphiroa, Lamouroux, 1812, p.A86. 



Thallus erect, usually arising from a small basal disk, terete or more or less flattened, 

 segmented, dichotomouslyj trichotomously, or verticillately branched, strongly calcified 

 except at the more or less elongated joints; composed of elongated cells arranged in 

 superimposed transverse zones surrounded, except at the joints, by a layer of smaller 

 cortical cells; conceptacles small, scattered over the surface of the segments, immersed 

 in the cortex or more or less prominent, opening by apical pores; tetrasporangia zonately 

 divided. 



About 30 species, in warm seas. 



KEY TO SPECIES. 



Segments of thallus terete or nearly so, frond strongly calcified and very brittle . i . A . fragilissima (p. 526). 

 Segments of thallus decidedly flattened, often two or three times as broad a*s thick, frond less 

 calcified and less brittle 2. A . brasiliana (p. 527). 



i. Amphiroa fragilissima (Linnaeus) Lamouroux. PI. CXII, fig. 40. 



Corattina fragilissima, Linnaeus, 1758, vol. i, p. 806. 

 Amphiroa fragilissima, Lamouroux, 1816, p. 298. 

 Amphiroa fragilissima, De Toni, 1905, p. 1808. 

 P. B.-A. No. 2198. 



Fronds forming tufts, 2 to 5 cm. tall, about 0.2 to i mm. in diameter, usually terete, sometimes flat- 

 tened, especially toward the apices, branching dichotomous, sometimes irregular, segments 6 to 14 

 diameters long, usually 8 to 10 diameters, sometimes locally swollen; conceptacles scattered over the 

 surface of the segments, inconspicuous; color pinkish white, becoming white when dried; texture 

 very fragile. 



West Indies; Peru. 



Occasional on Bogue Beach, Beaufort, N. C., summer and autumn, 1903 to 1905 ; one plant Shackle- 

 ford jetty, August, 1905; about 10 tufts, coral reef offshore, May, 1907. 



The specimens from the coral reef and the plant from Shackleford jetty seem to agree with this 

 species from other localities, except that they show slightly greater flattening. Some of the specimens 



