AEX. 12 HEXACTINELLID SPONGES — OKADA 71 



the sponge body. The diaetins measure 3 mm long and 170/x broad 

 at the center. They are of nearly the same breadth throughout, but 

 taper suddenly near the sharply pointed ends, which have the sur- 

 face roughened. Except the ends, the entire surface is quite smooth 

 and completely covered with numerous striations. Single spicules 

 occur irregularly. 



The comitalia are only 12/a thick or sometimes less, showing as 

 usual the same breadth for the greater part of their length. 



The prostal marginalia are long diaetins of variable sizes, project- 

 ing from the oscular edge and measuring 15 mm to 40 mm in length. 

 They taper gradually toward the conically pointed ends, of which 

 the distal one is smooth, while the proximal is rough. Further- 

 more, the prostal marginalia project from the surface of the superior 

 regions of the entire stock. Most of the hypodermalia are moder- 

 ately large oxypentactins with smooth, tapering rays, except at the 

 end. The straight, unpaired proximal ray tapers strongly toward 

 the sharply pointed and microtuberculated end and is 3 mm long. 

 The paratangential rays are shorter or nearly the same length as the ' 

 proximal ray, usually 1 mm to 1.5 mm. They are always either more 

 or less curved or nearly straight, tapering gradually toward the 

 conically pointed and sparsely tuberculated ends. These spicules 

 may occur singly or grouped together. The paratangentials consti- 

 tute the beams of the irregularly meshed hypodermal latticework. 



The dermalia are mostly stauractins and pentactins, occasionally 

 hexactins. 



The pentactins are commonly supplied with a bosslike rudiment 

 of the distal sixth ray. The paratangentials measure SO/x, to 100/a in 

 length (measured from the center) and S/x in thickness at the base. 

 The proximal rays are in general nearly as long as, or longer than, 

 the paratangentials, measuring 100/x. to 200/x,. They taper perceptibly 

 from the base toward the conically pointed end. The surface is beset 

 throughout with microspines, which grow considerably weaker and 

 thinner toward the base of rays and central node. In the stauractins 

 (fig. 7, h) the bosslike rudiment is usually not present. The axial 

 rays are IDO/i, to 240/a in length and roughened all over. The micro- 

 spines on the surface are more pronounced on the conically pointed 

 ends. In the hexactinic form, the proximally directed ray is not so 

 long as in the gastral hexactins, and is nearly as long as the paratan- 

 gentials of the same spicule. 



The gastralia (fig. 7, a) are all rough hexactins in which the free 

 proximal ray is usually much longer than the other rays. In length 

 the paratangentials measure 140ju, to 160/*. The distal ray is fre- 

 quently shorter than, though occasionally as long as, the paratangen- 

 tials. The proximal ray is 210/* to 280/i long and 12/i broad at base 



