234 I- IJIMA : HEXACïINELLTDA. I. 



Frequently, but not always, the distal ray is slightly swollen near 

 the end, presenting a club-like shape (fig. 18). All the other 

 rays are tapering toward the pointed end and nearly smooth all 

 over or snbterminally obsoletely tubercled. — The distal ray is 

 usually 80-150 n long ; sometimes as short as to measure only 

 50 /i in length. The paratangential rays are 175-275 mm. long. 

 In the strength of the rays, as also in the manner of arrange- 

 ment of the dermalia, there obtains a noteworthy difference in 

 different parts of the sponge surface. 



Slender-rayed are the dermalia in the depressed areas 

 around the parietal oscula (figs. 17, 18). The rays measure 

 about 6^/2 IJ- ill average breadth near the central node. The 

 paratangentials are arranged so as to form a tolerably regular, 

 quadrate meshed latticework, with meshes 150-300 n in length 

 of sides. Whereas, on the parietal ledges, there occur on the 

 whole somewhat larger and much stouter dermalia (figs. 14-10, 29), 

 though these are by no means of uniform strength. On an 

 average, the rays are here about 12 // thick near the spicular 

 center. The larger dermalia seemed to increase in number as 

 they approach the edge of the ledges, although even in this part 

 there may occasional!}^ be intermingled such as are as weakly 

 developed as any in the entire dermal system. Moreover, the 

 dermalia occur on the ledges irregularly crowded, so that a re- 

 gularly meshed latticework is not brought into formation. 



The greatest development is attained by the dermalia along 

 the free edge of the cuff (Pi. VIII, fig. 13). They may not 

 inappropriately be called the prostalia marginalia. The shape is 

 sword-like. Total length up to 2\l.2 im«. The rays reach up to 

 45 f^ in breadth near base ; all of them taper towards the pointed 

 end. The free distal ray may be 800 /^ long ; it is beset for the 



