POLYPS AND CORALS. 41 



summit, and in young specimens reaches the margin. Septa 

 in four cycles not crowded, diminishing in width and thick- 

 ness according to their orders, projecting somewhat above 

 the walls, broadly rounded at top and nearly perpendicular 

 within, the primaries reaching about half way to the center ; 

 the secondaries little narrower, the surface of all strongly 

 granulated. In front of all the septa, except those of the 

 fourth cycle, there are prominent, thin, rather broad, and 

 usually undulated, paliform lobes. Columella small, sunken, 

 composed of about twenty papillae. 



Height of largest specimen .2 inches; diameter of 

 cup .18; depth .1. 



Ebon Island, on Stylaster elegans nob. H. Mann. 



Young specimens .15 inch in diameter have a complete 

 epitheca, septa not projecting, toothed and not rounded at 

 summit, pali more slender, and columella relatively more 

 developed. 



Hetbrocyathus alternata Verrill, these Proceedings, 

 vol. iv, page 149, April, 1865. 



Plate 2, figures Q and Q a. 



Base attached to a small univalve shell, which it entirely 

 covers and nearly conceals, forming thus a broad, flattened 

 base more than half the diameter of the disk ; above the 

 basal region, which is covered with small granules and 

 scarcely costate, there is a slight constriction, beyond which 

 the walls spread obliquely outward to the edge of the disk; 

 this part of the wall is strongly costate, the costae being 

 alternately very unequal, much thickened and strongly gran- 

 ulated. Septa in four cycles ; those of the first broad and 

 considerably exsert, with the upper edges evenly rounded 

 and entire, inner border perpendicular, sides strongly gran- 

 ulated ; those of the second cycle are nearly as broad and 

 similar in form ; those of the third and fourth cycles succes- 

 sively narrower. Paliform teeth exsert before all the cy- 

 cles except the last, but are largest before those of the sec- 

 ond. Columella very little developed, papillose, scarcely 



COMMUNICATIONS ESSEX INST. VOL. V. 6. JULY 2, 1866. 



