G4 ART. 7. T. IJIMA ! HEXACTINELLTDA, IV. 



The (Jeriiialia nvo rongli pentaetins ; occasionally stanractiDs 

 (TM. TV., figs, !2 & 3). The rays are on an average 130 ti long 

 as measnred from the center and 7.6 //. thick. They scarcely 

 taper outwards at all or do so in T)nt a slight degree. The ends 

 are rounded. Not infrequently the pentactinic form, in which 

 the un]mired ray is always directed proximad, shows an indica- 

 tion of the sixth distal ray in the form of a knob. The para- 

 tangential cross is usually — hut not always — more or less convex 

 on the outside, which is due more to the rays concerned being 

 not (juite at right angles to the radial axis, rathei- than to the 

 cnivalure of the rays themselves. Seen surf ice on, the delicate 

 (Iciinal latticework (PI. IV., fig. <>) presents irregular meshes, 

 though in places these show a tendency to assume a regular 

 quadrate arrangement. Here and there occur unusually small and 

 slender-rayed dermalia — in all probability not fully developed — in 

 which the rays are but obsoletely rough and run out to fine 

 points. 



On the thin oscular margin the dermalia present are all 

 stauractins. These and some thin diactinic ]iarenchymalia seem 

 to be nearly all the spicules that enter into the support of that 

 part. 



The gaslralia are pentactins, but sometimes stauractins and 

 rarely even diactins. The rays are characterized similarly to 

 those of the dermalia ; only they are frequently of a nuich great- 

 ei- length, while the microtubercles of the surface occur somewhat 

 more sj)ai'sely. Without forming a continuous layer the spicules 

 in (piestion are irregularly distributed over the choanosonial sur- 

 face facing the gastral cavity. 



