REPORT ON THE HEXACTINELLIDA. 315 



however by any means form a regular lattice-like framework with cubical mesh-spaces. 

 A framework with predominantly three-sided meshes is in fact formed, on the one hand 

 by the diversion of some rays from their original position at right angles to one another, 

 on the other hand by quite irregular fusion of the rays of adjacent hexacts. In older 

 portions these meshes appear distinctly compressed and rounded. The surface of the 

 beams may be completely smooth, or may be roughened by the development of more 

 or less numerous small pointed tubercles. The pegs projecting outwards towards the 

 dermal membrane, or inwards towards the gastral membrane, are always beset with 

 numerous tubercles and are frequently swollen in a knob-like manner. While the freely 

 projecting dermal pegs are usually straight, that is to say, usually stand at right angles 

 to the surface, the projecting pegs on the gastral side are found to be mostly incurved or 

 thickened into short knobs (PL LXXXIV. fig. 1). The ends of the free rays of the 

 dictyonalia which project from the surface of the septa into the lumen of the meshes 

 also exhibit rough conical pegs which are seldom directed quite at right angles to 

 the wall of the canal, but project as a rule obliquely. 



The dermal skeleton consists of hexacts which form a regular quadrate network and 

 are provided with a fir-tree-like distal ray (PI. LXXXIV. fig. 8), and very variously 

 formed scopulse. The four equally long transverse rays, as well as the usually distinctlj^ 

 shorter proximal ray of the dermal hexacts, are either smooth or somewhat rough on the 

 truncated extremities. 



In the dermal scopulse I observe that the shaft, which is of variable length, runs out 

 at the inner extremity to a point, while the outer extremity, which is moderately swollen, 

 or more rarely provided with a knot-like thickening, gives ofi" four (more seldom three or 

 five) prongs which either terminate in a point or are provided with a knob-like or club- 

 like terminal expansion. Both on the pointed extremities and also on the terminal 

 clubs or knobs small lateral barbs usually occur (PL LXXXIV. figs. 4, 5). The branches 

 of most of the scopulae possess the usual length of about 0'07 mm. Scopulae also occur 

 here and there which have the branches twice as long, and either terminate in j^oints with 

 small smooth knobs, or are beset beneath the extremity with small barbs (PL LXXXIV. 

 figs. 3, 5). 



In contrast to the Dictyonina hitherto described, the gastral skeleton of Aphrocallistes 

 ftocagrei diff'ers very essentially from the dermal. On the surface of the gastral wall I finil 

 neither hexacts nor pentacts, nor any trace of scopulse, but only diacts of variable length, 

 more or less rough, sometimes even pronged, with rounded extremities and central knots 

 variously developed. These diacts lie properly in the gastral membrane, but they also 

 extend into the subgastral space, and seem not unfrequently to fuse with the projecting, 

 but frequently incurved and club-like swollen pegs of the dictyonal framework. 



The loose parenchymalia include the uncinates, which are disposed at right angles 

 to the bounding surface, and vary greatly in length and strength. The inner extremity 



