24 PROCEEDINGS OF THE NATIONAL MUSEUM yol. 81 



siderably shorter than the radial ray, which measures 0.4 mm to 0.7 

 mm or more in length. All the rays are smooth over the entire 

 surface and attenuated gradually toward the pointed ends. 



In both specimens the acanthophores (fig. 2, e, /) near the lower 

 end of the body are clearly chiefly composed of cross-shaped tetrac- 

 tins and large straight diactins. In specimen A, the diactinic acan- 

 thophores are most numerous, with a few tetractinic ones mixed in; 

 while in specimen B, the latter are the more numerous. All the 

 superficial diactinic acanthophores are covered with uniformly de- 

 veloped, robust, short spines and have the appearance of being cov- 

 ered with crystallized sugar. The basal parts of the tetractinic 

 acanthophore are mostly smooth, frequently straight, and bear spines 

 on the somewhat inflated, terminal parts of the rays only. 



The diactinic marginalia (fig. 2, a, h) forming the fringe of the 

 oscular margin and the margin of pores on the sieve plate are not 

 more than GOO/x to 850fi long. The proximal ray of these spicules, 

 which is imbedded in the body of the sponge, is perfectly smooth; 

 the distal free ray, resembling a Lombardy poplar in shape, meas- 

 ures SOfjL to 40/A broad, is covered with oblique spines, and has a dis- 

 tinct distal spine. The center of the spicule bears four rounded pro- 

 tuberances arranged crosswise and containing rudiments of axial 

 canals. 



The dermal oxypentactinic pinules (fig. 2, c) sparsely cover the 

 strands of the external network. Their four basal rays, which form 

 a rectangular cross, are lOju in thickness, 35/;i to 50/x long, terminally 

 pointed and finely granular. Their free radial ray varies from 

 240/^ to 280ix in length, is smooth on the proximal third, uniformly 

 attenuated toward the sharp-pointed end, and covered with obliquely 

 directed spines on the distal two-thirds. The spines attain the 

 greatest length near the lower end of the distal spined part of the 

 ray; upward they gradually decrease in size. 



The canal a r pinules are nearly similar, a little shorter, not more 

 than 200/i long, and slenderer and covered with fewer spines. They 

 occupy the walls of the larger incurrent canals but do not stand 

 nearly so close together as the dermal pinules on the external 

 surface. 



The pinules of the oscular sieve plate are a little shorter in the 

 distal radial ray, measuring 200/x long and 20/a to 30/a broad ; they also 

 resemble a Lombardy poplar. The basal cross measures 80ju, to llO^u, 

 in length and is finely roughened by the presence of microspines. 

 These spicules are distributed much more closely together. 



The dermal macramphidisks (fig. 2, g) vary in length from 200/^ 

 to 320/j,. The shaft is 2/x to 20jli broad and usually bears rounded 



