254 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxn. 



Coralluni of light texture, but of massive growth-form. Upper 

 surface irregularly convex, with gentle undulations and some large 

 humps; lower surface concave, with irregular, concentric corrugations 

 and an epitheca that extends almost to the edge. Greatest length, 

 128 mm.; width, 67 mm,; height, 70 mm.; thickness of living portion, 

 up to 25 mm. 



Calices usually with slightly elevated margins, varying in height 

 from a small fraction of a millimeter to 1 mm. ; in some instances not 

 raised above the exothecal surface. Their diameter from 1.5 to 2.5 

 mm., usually from 1.8 to 2 mm. Distance apart from 1 to 3 mm.; on 

 the upper portion usually about 1.5 mm. ; near the edges more distant. 

 The calices are generally smaller and more crowded in the depressions; 

 larger and more distant on the convexities. 



The septa form three complete cycles, the primaries and secondaries 

 reach the columella, but the former are slightly thicker; the tertiaries 

 are short and thin, almost rudimentary. The outer ends of the septa 

 are continued beyond the corallite wall and form distinct, rather acute 

 costa>, alternating in size. The septa are thicker in the mural ring, 

 becoming thinner outwardly toward the costal edges and inwardly 

 toward the inner ends. The margins are exsert, steeply arched, the 

 primaries and secondaries exceeding the tertiaries in height; the sum- 

 mit of the arch very obscurely dentate or entire, the inner and outer 

 edges distinctly dentate; near the columella there are rather long teeth. 

 The septal faces are densely granulated. Calicular fossa of moderate 

 depth, about 1.5 mm. Columella vesiculate, very well developed, join- 

 ing the inner ends of the primaries and secondaries. 



In longitudinal sections of the corallites, the septa show numerous, 

 irregularly disposed perforations, and many very delicate dissepiments. 



The corallites are joined by a very vesicular exotheca, whose upper 

 surface is composed of numerous blistery elevations that bear a great 

 many small, pointed spines. In a section of the corallum the exothecal 

 vesicles are seen to occur in rather definite zones, about 0.5 mm. apart, 

 the upper of any two zones being supported by the spines of the lower 

 one. 



ReniarJi'x. — A second specimen of CyjjJiastrea.,^' which I believe should 

 be referred to the same species, differs in a few particulars from the 

 specimen just described. The dift'erences are contained in the follow- 

 ing notes: 



Corallum of somewhat deformed, ellipsoidal shape, with calices dis- 

 tributed over its entire surface. Length, 67.5 nmi.; greater diameter, 

 55 mm. ; lesser diameter, 54 mm. 



Calicular margins practically level with the exothecal surface, or 

 slightly elevated above it, in one extreme instance about 1.3 mm. tall, 



aCf. Plate XX, fig. 2, and plate XXII, figs. 1, 3. 



