ART. 12 HEXACTINELLID SPONGES — OKADA 87 



proximal raj', T5/i to SO/x. All the rays taper very perceptibly to- 

 ward the conically pointed ends. Their surface throughout is beset 

 with conical, erect, or nearly erect microspines, which are sometimes 

 absent on the base of the rays and on the central node. Both of these 

 parts are smooth. The microspines on all rays are strongly directed 

 toward their ends. The meshes of the latticework for the greater 

 part appear quadrate, measuring 110;u, to 143;u, in length of sides. 



The gastralia are also hexactins (fig. 11, c), of nearl}^ the same 

 shape as those of the dermal layer, but on the whole much larger. 

 The length of the rays, as measured from the spicular center, is 

 usually 155ju. to 180/a. The six rays are nearly the same length, 

 but often the distal ray is shorter than the others, measuring 120/a 

 to 165jit in length. Except at the base of the rays and on the central 

 node, both of which parts are generally smooth, the surface is also 

 beset with numerous microspines similar to or somewhat more weakly 

 developed than those on the dermalia. Stauractins are rough near 

 the ends and either nearly plane or slightly arched. They are of 

 rare occurrence among the gastralia. The rays, perceptibly taper- 

 ing toward the rounded tij), are nearly all uniformly thick, though 

 sometimes slightly swollen at the center. 



Oxyhexasters are commonly represented by hexactinic forms, and 

 somewhat less frequently by hemihexactinic and normal forms. The 

 former two are abundantly present in the hypodermal, hypogastral, 

 and parenchymal layers, especially the hexactinic form, which is 

 much commoner everywhere. Two forms of normally developed 

 oxyhexasters are occasionally found in the endosome and in the 

 choanosome. In the endosome, the delicate oxyhexasters (fig. 11, i) 

 are rarely intermingled with common robuster forms. These robuster 

 normal oxyhexasters (fig. 11, j) measure 90/x to llOpi in diameter. 

 Two to four stouter terminals with slightly rough surface, measur- 

 ing 52/x in length and widely diverged, are attached to the broad prin- 

 cipals which measure Qfx in breadth. Hexactinic forms (fig. 11, e) 

 are very abundant throughout. They have six broad, strong rays, 

 45/x to CO/x long, which taper strongly toward the sharply pointed 

 end, measuring 4/x to S/x at the base. The entire surface is slightly 

 rough and tuberculated, except at the base. Besides this form much 

 smaller hexactinic forms (fig. 11, g, h) with the surface entirely 

 smooth, occasionally occur, in all probability a partly developed, or 

 3^ounger, form. The hemihexactinic form (fig. 11, f/, /) may be 

 present together with the hexactinic form. They show nearly the 

 same features, with big rays, as those occurring in other members 

 of the genus, measuring 90jli to lOO/i. in diameter. 



The macrodiscohexaster (fig. 11, I) shows a regularly spherical 

 form, measuring 230;a to 320ja in diameter. From a central sphere 

 55/A to 75/x across, there arise numerous straight, smooth-surfaced 



