Original diagnosis : Corallum thin, partially explanate, attached and incrustiiis at the centor, the- edges free and nearly horizontal for a width of 4 inches or more. The corallu m at half an inch from the edge is 0.1.5 of an inch [3.75 mm.] thick; at 3 inches, 0.30 [7.5 mm.] ; texture very porous, but tolerably firm. The lower surface is destitute of papilliform processes, and nearly even, composed of a very porous spongiform tissue, roughened with minute sharp points. The cells are very small (0.01 in. =0.25 mm. ), regular, wholly immersed, surrounded bya circle of small spinules, thickly scatteredd over the surface, except toward the edge, when they are generally more distant and often larger, usually with 12 very small, rudimentary septa. Upper surface very porous, somewhat undulated, a little uneven, thickly covered with small, unequal prominent, round-topped papillae, which have a very open spongiform texture, their surface covered with rough projections. Sometimes these papillae are less developed and appear like small rounded clusters of spongy trabiculae, which project all over the surface, and are laterately divided. Cells thickly scattered over the surface, each usually surronded by a cluster of four or live of the larger papillae, considerably larger than those of the lower side (about 0.03 of an inch=0.7mm).l, with six quite distinct septa, which extend about one-fourth across the cells. Toward the central part of the coral the cells are generally somewhat larger and have 12 septa, six very narrow ones of the second cycle alternating with the six larger primary ones. Close to the edge the papilae sometimes form radiating rows, or unite into short, thin ridges. The largest papillae are scarcely 0.02 of an inch [0.5 mm.] in diameter, and about 0.04 [1 mm.] in height.