POLYPS AND COEALS. 87 



twelve, six well developed and a little thickened, alter- 

 nating with six very narrow ones. The upper surface of 

 the frond is covered, on the lower part, with very unequal, 

 densely crowded, slender, round-topped papillas, which 

 are mostly united in irregular clusters ; towards the upper 

 part of the fronds the papillae stand in vertical rows or 

 clusters, which near the margin unite and form thin, ele- 

 vated costse or crests, the edges of which are divided more 

 or less into thin and compressed, or round and slender 

 papillae, which have rounded summits, sulcated sides, and 

 a minutely roughened surface. The cells of the upjDer 

 side are not numerous, distantly scattered among the 

 papillae and between the crests, quite small and inconspic- 

 uous, but larger than those of the lower surface ; diameter 

 about .02 of an inch. Their septa are well developed, as 

 in those of the lower side. 



The only specimen seen is about four inches in breadth 

 and the same in height, the free portions of the frond 

 risinof about two inches. It encrusts the branches of a 

 dead Madrepora. 



Loo Choo Islands. Rev. S. W. Williams. Museum of 

 Yale College. 



This species is allied to M. foliosa, M. exesa, M. grand- 

 ifolia. The cells are, however, much smaller than in 

 either of those species, especially upon the lower side, 

 and its texture is more firm and solid, while its lower sur- 

 face is more papillose. Its upper surface is quite unlike 

 any except M. exesa, but even that species has the 

 papillae more regular and the surface more distinctly 

 divided into areolations by the elevations, while the 

 papillae themselves are much shorter, thicker, more obtuse, 

 and more completely united. 



MoNTiPOEA PATULA Yerrill, sp. nov. 



Corallum thin, partially explanate, attached and en- 

 crusting at the centre, the edges free and nearly hori- 

 zontal for a width of four inches or more. The coral- 

 lum at half an inch from the edge is .15 of an inch thick ; 

 at 3 inches, .30 ; texture very porous but tolerably firm. 



