366 BULLETIN" 103, UNITED STATES NATIONAL MUSEUM. 



in the Hunterian Museum at that institution, and I have based the 

 following description on them: 



The corallum is head-shaped, with a greater diameter of 107 mm. 

 and a lesser of 86. 



The calices are circular, 2 mm. in diameter, margins slightly ele- 

 vated, joined by equal costae, distance apart usually about 1 mm., 

 occasionally 2. 



Septa 24 in number, alternately larger and smaller; the larger are 

 rather thick and reach the columella ; the intermediate ones are short 

 and their inner ends are free. 



Columella spongy, well developed, its diameter about one-third 

 that of the calice. 



A comparison of the photographs with specimens shows that the 

 traditional Orbicdla annularis of the Caribbean and Gulf region is 

 correctly identified. 



There are in the collection of the United States National Museum 

 a number of specimens that are almost duplicates of the type-speci- 

 men, except that they are not worn, as is the type. These specimens 

 form the basis of the succeeding description (see pi. 81, figs. 1, la). 



The corallum forms rounded masses rising above a rather large, 

 firmly attached base, which is, however, less in diameter than the 

 maximum diameter of the corallum. Frequently there is a pro- 

 jecting or incrusting edge whose lower surface is covered by epitheca. 

 The upper surface may be uniformly rounded, undulate, or lobed. 

 The size, of course, is variable; the masses may be several feet in 

 diameter. 



The calices are circular, or slightly deformed. Their diameter, 

 measured between thecal summits is from 2 to 2.5 mm. In depres- 

 sions on the surface they may be smaller, about 1.5 mm., but these 

 are abnormal. Their edges are from 0.5 to almost 2 mm. apart, 

 about 1 mm. is probably an average. The calicular edges are 

 slightly elevated. The intercorallite areas are costate. Costae cor- 

 respond to all septa; subequal or alternating in size, those of adjoin- 

 ing calices meeting; edges dentate; thicker than the width of the 

 intercostal spaces and moderately elevated. 



Septa in three complete cycles, primaries and secondaries equal, 

 rather stout, extending to the columella and fusing to it; tertiaries 

 shorter, about half the length of the primaries, somewhat thinner, 

 inner edges free. Margins of the primaries and secondaries decid- 

 edly exsert; their inner edges fall perpendicularly to the bottom of 

 the calicular fossa, and bear just above the columella one or two 

 prominent teeth, with a few smaller teeth above; the septal arch is 

 either very gentle, obtuse, or it may be truncate, its dentations fine; 

 the outer margins steep, but more inclined than the inner, dentations 

 relatively coarse. Septal faces finely granulate; in longitudinal 

 cctions, the inner edges are lacerate, the last cycle with perforations. 



