POLYPS AND CORALS. 35 



Prionastrea Chinensis Verrill, nov. 



Corallum broad, explanate, somewhat convex above and 

 with irregular protuberances ; below incrusting at the cen- 

 ter, at the edges unattached and covered by a complete epi- 

 theca strongly marked with concentric lines of growth, and 

 extending to the edges. Thickness of coral about half an 

 inch, becoming as thin as .08 near the margin. Cells about 

 .35 of an inch in diameter, rather shallow, less deep than 

 wide, center depressed much the lowest, and having a papil- 

 lose columella composed of from six to twenty slender 

 teeth-like processes ; paliform teeth well marked, making a 

 prominent circle around the central space, rather stout and 

 lacerate at the ends. Septa about 32 or 34 in number, sub- 

 equal, except some small ones of the last cycle, not crowded, 

 narrowed within and deeply serrate with numerous spine- 

 like teeth, which are themselves often lacerate, or divided 

 at the ends into several slender, sharp teeth. Paliform teeth 

 much larger and stronger than the rest. Walls for the 

 most part thick and rounded ,• on the protuberances often 

 simple, thin and compact. 



Color of the unbleached coral deep yellowish-brown. 



HoDg Kong, Dr. Wm. Stimpson. 



Plesiastrea indurata Verrill, nov. 

 Flate 2, figure 7. 



Corallum broadly incrusting, convex above. Corallites 

 oblong, oval and irregular in form and size, scarcely promi- 

 nent above the general surface, rather crowded. Cells deep 

 and narrow. Columella loose, spongy. Paliform lobes, 

 slender and prominent, but scarcely visible except in a ver- 

 tical section. Septa in four complete cycles, perpendicular 

 within, broad and rounded at the summit, evenly and finely 

 denticulate, thick and closely crowded, scarcely exsert, those 

 of the last two cycles much narrower than the others. Cos- 

 tge prominent, very thick, those of adjoining corallites often 

 coalescing. Interstitial spaces nearly flat. The buds ap- 

 pear irregularly between the cells. 



