TRIBE III. MADREPORACEA. 567 



cettis paulo excavatis, vix '" latis,fundo plan-is, septis tenuibus, filifor- 

 mibus, scepe superne productis (super -fide itaque reticulata). 



Incrusting, | of an inch thick, undulate, margin subacute, often flexed 

 upward, and free for a third of an inch ; under surface smooth, or 

 obsoletely plicate. Corallum having the cells shallow, and often 

 prominent in minute, thin ridges, which give the surface a reticu- 

 late appearance. 



Plate 56, fig. 2, corallum, natural size. 







Feejee Islands. Exp. Exp. 



24. PORITES RETICULOSA. (Dana.) 



P. incrustans, undukita, margine vix libero, superficie mammillata, sen 

 tuberosa. Corallum porosissimum, cellis bene angulosis, paulum ex- 

 cavatis, grandioribus (%'"), f undo plants, septis tenuibu.s, scepe superne 

 productis. 



Incrusting, undulate, margin scarcely at all free, surface mammillate 

 and tuberose. Corallum very porous, cells neatly angular, shallow, 

 rather large (| of a line), plane at bottom, septa thin, and often pro- 

 minent in thin ridges, like the lichen. 



Plate 55, fig. 1, corallum, natural size. 

 Feejee Islands. Exp. Exp. 



25. PORITES ARENACEA. (Lamarck.) 



Incrustans, simplicissima. Corallum cellis super ficialibus, subconcavis, 

 perparvis. 



Incrusting, quite simple. Corallum having the cells superficial, sub-- 

 concave, very small. 



The Red Sea, incrusting the Mytilus margaritiferus. Lamarck. 



