510 Yerrill, N'otes on Radiata. 



Rhizopsammia Verrill, gen. nov. 



Corallum compound, low, encrusting, extending by stolon-like 

 expansions of the base, from which buds arise. Corallites cylindrical, 

 or nearly so, connected by thin creeping extensions of the base, which 

 have the same porous texture as the wall. Polyp-cells subcircular or 

 elliptical. Septa thin, crowded, a little projecting, arranged in four 

 or five cycles, those of the last cycle well developed, uniting to those 

 of the preceding cycle, which rise up in the form of prominent pali- 

 form lobes, beyond which the central region of the cell is deep. Col- 

 umella very porous, its surface papillose. Walls very jDorous, destitute 

 of ejjitheca, with scarcely distinct costoe, but with series of rough 

 granules. 



This genus among Madreporacea corresponds to Astrangia among 

 the Oculinacea, in its mode of growth. The paliform lobes are also 

 peculiar. 



Rhizopsammia pulchra Verriii, sp. nov. 



Corallum composed of clusters of corallites irregularly grouped on 

 the surface of a stone. Corallites united only by the thin basal expan- 

 sions, mostly placed at distances about equal to their own diameters, 

 low, but variable in height, base as broad as summit, or broader. 

 Walls thin, very porous, subcostate, the ridges nearly equal, with two 

 or three rows of sharp rough granules, the grooves between deep, but 

 narrow, with small, interrupted, deep pits or pores. Polyp-cells sub- 

 circular or elliptical, deep at center. Septa well developed, in four 

 complete cycles with some of a fifth, thin, crowded. The primaries 

 and secondaries nearly equal, slightly projecting above the margin, 

 rounded at top, inner edge perpendicular, roughly denticulate, the sides 

 roughly granulous ; those of the third cycle thickened outwardly, and 

 united by spongy tissue with the adjacent ones ; septa of the fourth cycle 

 thin, bending toward and soon uniting to those of the third, which 

 beyond the point of union rise al)ruptly in the form of prominent 

 paliform lobes, beyond which the inner edge is nearly perpendicular 

 to the columella, and rudely denticulate, the sides roughly gi-anulous. 

 Columella, moderately developed, papillose at surface. Color of 

 the unbleached coral reddish. 



Height of larger corallites "15 to -20; diameter *15 to "25 ; depth of 

 cells -10 to '13 of an inch. 



Pearl Islands, at extreme low-water, — F. H. Bradley. 



Upon the same small stone, there were, with this species, specimens 

 of Ulangia Bradleyi, Astrangia dentata^ A. pulchdla^ and a new 

 species of Paracyathus. 



