AKT. 12 HEXACTI^STELLID SPONGES — OKADA 53 



processes protrude from the dermal and gastral surface. The beams 

 composing the net are nearly smooth and measure 20/a to 40/x broad. 

 The nodes are very slightly or not at all thickened, and are only 

 sparsely covered with small tubercles. 



The dermalia are strong hexactins, with a free distal ray 180//, to 

 200fi long. They are terminally thickened in a club-shaped manner 

 with stout spines, or thorns, of medium length, which diverge ob- 

 liquely and are curved tovrard the end of the ray like the branches 

 of a Lombardy poplar. The tangential rays are simple, straight, 

 strongly tuberculous at the conically pointed ends, and much shorter 

 than the distal ray, measuring 130|U, to 150/^ in length. The proximal 

 ray is similar in shape but generally somewhat shorter. These hex- 

 actins are arranged regularly in quadratic meshwork, formed by the 

 paratangential raj^s of the spicule. 



The gastralia are stout, straight, occasionally slightly curved, 

 somewhat flattened diactins, with a defined swelling at the center. 

 Their ends are conically pointed or infrequently rounded and covered 

 densely with small pointed tubercles. The spicule is always covered 

 with such protuberances in its entire remaining length. The length 

 of spicule varies considerabl3^ measuring from 0.8 mm to 1.2 mm or 

 more in length. The spicules are irregularly scattered on the gastral 

 layer. 



Scopulae are numerous, arranged perpendicularly to the surface or 

 scattered irregularl}^ in the parenchyme and sometimes distributed 

 perpendicularl}^ to the wall of the incurrent canals. The four to six 

 branches of the scopulae perpendicular to the surface of the sponge 

 lie between the proximal rays of the dermal hexactins and do not 

 reach the sponge surface, except the extremity of the proximal ray. 

 Elsewhere in the sponge they have no definite arrangement. The 

 shaft is generally simple, straight, 160/a to 210/x long, and gradually 

 tapering toward the pointed end. It is always slightly rough on the 

 surface except at the end, which is frequently smooth. The number 

 and shape of the branches are subject to considerable variation. 

 Usually four stout or slender diverging dermal branches are observed. 

 They arise from a comparatively short thickening at the distal end 

 of the shaft and extend upward toward the distal ends, being nearly 

 parallel to one another. They are nearly cylindrical, slightly thick- 

 ened in a knot-shaped manner at the distal end, and uniformly 

 densely covered in their entire length with very minute spines 

 directed obliquely back^vard. The terminal thickening is covered 

 with similar but slightly stouter spines. 



The other kinds of scopulae occasionally found on both layers 

 differ mainly in length from the one described above. They are 

 aljout two or three times as long as the former scopulae, measuring 

 MOfi long in shaft and 80/^ long in dermal branch. 



