REPORT ON THE HEXACTINELLIDA. 131 



parenchyma includes small rosettes in varying abundance and irregular distribution. One 

 of these forms admits of the designation plumicome. Each of the six simple cylindrical 

 principal rays bears a small plano-convex transverse disc, from which very fine S-shaped 

 terminals arise in concentric rows in perianth-like fashion, very much as in the plumicome 

 of Poli/Iophus philipinncnsis represented in PI. LIV. figs. 4, G. Finally, there are very 

 minute isolated rosettes, in which the short simple principal rays bear terminal transverse 

 discs, having a thick brush-like fringe of somewhat long and very thin, radially disposed, 

 knobbed terminals, like those in the rosette of Rossella antarctica, figured in PL LV. 

 fig. 6. 



I must further note that I was not able to find these two extremely delicate and 

 inconspicuous forms of spicules in all the specimens which I examined, but only in a few. 



The hj'podermalia are simple smooth oxypentacts in which the unpaired proximal 

 ray is always straight and somewhat long, and penetrates radially, like a nail, far 

 into the parenchyma. The four tangential rays, intersecting at right angles, extend 

 close beneath the dermal membrane, corresponding to the curvature of the general 

 sponge surface in exhibiting a more or less marked inward curvature (PI. LIII. 

 fig. 5). In the quadrate meshes, which are formed by the apposition of these tangential 

 rays of adjacent hypodermal pentacts, smaller pentacts of a similar type occur, with their 

 tangential rays disposed parallel or diagonally to the tangentials of the larger forms. 

 The dermal membrane itself contains exclusively numerous cruciate autodermal tetracts 

 in which the rays are more or less roughened, somewhat narrowed towards the extremity, 

 and ending finally in a conical point or in a slightly blunted fashion. 



At the lower somewhat truncate basis of the egg-shaped sponge, the hypodermal 

 oxypentacts are modified into long anchors by the thickening and more marked curvature 

 of the tangentials, and by the decided thickening and elongation of the proximal 

 tangential ray. These anchors are gradually more and more protruded from the sponge 

 body, and may serve for the attachment of the sponge to its soft substratum. At the 

 margin of the oscular aperture, I have sometimes observed long, pointed, rod-like needles, 

 projecting radially to a more or less marked extent. These may be fitly regarded as 

 marginalia. 



In the evidently much younger and completely closed spherical specimen, the skin 

 exhibits only hypodermal oxypentacts, and simple, strongly developed, cruciate auto- 

 dermal tetracts. Internally, between the simple oxyhexacts, moderately long oxydiacts 

 occur, with central nodes of intersection. Numerous discohexasters are also present 

 (PI. LIII. fig. 4). 



