THE SPONGES. 99 



The color is gray. The upper surface is comparatively even, but below 

 the level of the pore areas there are numerous rather vaguely marked 

 conulose eminences pointing downward. The surface in general is feebly 

 hispid with small oxeas, projecting obliquely for the most part about 1 mm., 

 but over the lower part of the sponge the projecting spicules, pointing 

 downward, are more abundant and are longer, reaching commonly a length 

 of 3 to 4 mm. A few compact bundles of spicules, scattered over the lower 

 surface, broken off close to the body, and measuring less than 0.5 mm. in 

 diameter, probably represent rootlets. 



The pore areas in general are indistinct, owing in part to the fact that 

 they lack a clearly defined lower boundary, and in part because the 

 margin scarcely differs in color and appearance from the rest of the 

 sponge sui-face. The upper margin of the areas nevertheless forms a 

 distinct ridge, which in some cases is drawn down so as to project 

 obliquely over the area. There is no spicular fringe. The pore mem- 

 brane lining the area presents the usual reticular appearance, except 

 where the pores are closed. The pores themselves measure up to 180 ju, 

 in diameter. 



The body of the sponge is not excavated by large canals, and is 

 accordingly comparatively dense. Flagellated chambers measure about 

 40 X 30 /A in diameter. 



Megasderes. 



1. Dichotriaene ; rhabdome, straight, tapering evenly, 5 mm. x 80 /i ; 

 protocladus, 280 fx. x 70 fj., tapering distad very slightly ; deuterocladus, 

 800 /A x 50 /A, tapering evenly and curved outward, then inward in the 

 fashion so common in species of Thenea. 



In the neighborhood of the pore areas, the dichotriaenes show the usual 

 modification, the cladomes becoming smaller, the deuterocladi especially 

 short and about straight. 



2. Proiriaene. Among the modified dichotriaenes round the pore areas 

 a few perfect protriaenes, resembling the spicule shown in Fig. 6, Plate 

 13, occur. 



3. Anatriaene. Only a single spicule was found. It was a somal 

 anatriaene resembling the smaller radical forms of Thenea lamelliformis. 



if. Oxea. The very numerous oxeas fall into three classes which inter- 

 grade. Types of the three classes measure respectively 8 mm. x 70 /x, 

 8 mm. X 17 /x, 1.25 mm. x 20 /ia. 



