SILICIOUS AND HORNY SPONGES WILSON. 443 



The surface is covered with closely set conuli, singly or in ridges, 

 between which there is smooth membrane. Oscula 4 mm. and less in 

 diameter, scattered over the sponge. Pores closed. Subdermal cavi- 

 ties underly the smooth parts of dermal membrane. 



Skeletal framework consists of ascending main fibers which are 

 compound (fascicled) and an intervening large-meshed irregular 

 network of simple fibers. The main fibers are 300-500 [x thick and 

 about 1-2 mm. apart. Each is made up of several compact elemen- 

 tary fibers, or funiculi, 50-100 [x thick, which lie close together, less 

 than a spicule's length apart; the funiculi fuse with one another here 

 and there, and are moreover connected together, sometimes by scat- 

 tered spicules but more generally by small spicular bundles that are 

 placed well apart from one another. The branches of the main fibers 

 diverge in obliquely radial directions and pass singly into the conuli, 

 where the funiculi are more intimately fused than elsewhere. The 

 fibers consist of closely packed smooth styles and a little spongin; 

 spongin not showing, or barely showing, on the outside of the funi- 

 culi. They are echinated with acanthostyles, but in many places 

 very sparsely, perhaps owing to imperfect preservation. 



The reticulum which stretches between the main fibers, is made 

 up of simple fibers 50-85 jx thick. The meshes vary in size and 

 shape, characteristic ones measuring 175 by 175 [x, 200 by 350 [x, 

 #00 by 350 jx, 250 by 500 tx. The fibers are made up of closely packed 

 smooth st}les and some spongin; there is little or no spongin on 

 the outside of the fiber, except at the nodes and round the bases of 

 the acanthostyles. The echinating acanthostyles are fairly common 

 in some regions, sparsely scattered in others; the differences may 

 he due to the preservation. 



Spicules. — 1. Skeletal style (pi. 49, fig. 7), smooth, slightly curved, 

 200-280 by 8-12 [x ; closely packed in skeletal fibers. 



2. Dermal style (pi. 49, fig. 8, a, &), smooth, nearly straight; a 

 great many about 100-120 by 3 [x, but they run up to 200-300 by 

 5-6 [x. Abundant in the dermal membrane, where they occupy, in 

 general, a tangential position; over the conuli, they project radially, 

 forming a furze, and elsewhere they may project in diverging tufts 

 (bouquets), although not densely enough to form a furze. 



3. Acanthostyle (pi. 49, fig. 7), 70-80 by 6 [x; head spinose and 

 slightly enlarged ; part of shaft near head usually less spinose than 

 the distal half. 



4. Isochela (pi. 49, fig. 8, c), palmate, small, 14-16 [x long, fairly 

 abundant in the dermal membrane and in the membranes of the 

 interior. 



5. Khaphides, as long as 200 (x but variable in length, although 

 always long and slender; slightly bent or curved in irregular fashion; 



