318 THE VOYAGE OF H.M.S. CHALLENGER. 



into the lumen of the canals. From an examination of the often vexy obviously marked 

 axial canals, it may be seen that the rays of adjacent dictyonalia are partly fused in the 

 familiar longitudinal fashion (somewhat as in Farrea), partly in a more irregular 

 arrangement, crossing one another arbitrarily, or connected at the intersections. Some- 

 times all the six rays are concerned in the formation of the network, which lies 

 approximately in one plane — an arrangement which is obviously only possible through 

 the great curvature of some rays. Usually, however, one ray is bent at right angles or 

 obliquely inwards, and is provided with a free point, which projects into the canals on 

 either side. Where the margins of three adjacent canals meet one another, the lattice- 

 like networks are slightly separated, and an irregular interspace is thus formed. 



As in Aphrocallistes hocagei, the dermal marginal pegs of the dictyonal framework 

 stand at right angles to the dermal membrane, while the longer gastral marginal pegs are 

 in part curved inwards. The pegs on the inner surface sometimes project obhquely 

 towards the dermal surface into the lumen of the canals, and are sometimes applied quite 

 close to the surface of the wall, but the free tuberculated end is always directed outwards 

 towards the dermal membrane. 



The beams of the meshwork often appear almost entirely smooth, while in other cases 

 they are more or less richly beset with small tubercles. The freely projecting pegs all 

 exhibit a rough or tubercled surface. 



The dermal skeleton is distinguished by the strong development of the distal fir-tree- 

 like ray of the dermal hexacts. This is richly pronged and more bushy than in the other 

 species of the Aphrocallistes. The numerous scopulse, which are present in the dermal 

 skeleton, exhibit a shaft which runs to a point beneath, and forks externally into two, 

 more rarely into three branches, after forming a simple expansion or an annular thickening. 

 The branches are rough on their outer extremities, and terminate either in a simple 

 rounded manner (PL LXXXV. fig. 7), or in a very slight knob-like thickening. 



In the gastral membrane, as in Aphrocallistes hocagei, the hexacts are replaced by 

 simple, straight, rough or pronged diacts of variable length, with rounded extremities and 

 central knots (PI. LXXXV. fig. 6) ; pin-like monacts are also scattered here and there 

 (PI. LXXXV. fig. 10). Whether the scopuljB, which are entirely absent in the gastral 

 skeleton of Aphrocallistes hocagei, occur in the present instance remains doubtful. It is 

 true that in the dried specimen and on the inner side of the cup-wall scopulae occur 

 which, like the dermal, consist of a terminally pointed shaft, and of two, more rarely 

 three knobbed and externally roughened branches, but I am not sure that these are not 

 subsequent extrinsic intrusions. 



The uncinates are distinguished by their length and also by the fact that their 

 greatest dilatation usually lies much nearer the dermal than the gastral extremity. 

 This latter appears much more slender, and usually runs out into a smooth (PI. LXXXV. 

 fig. 2) point, which is less frequently beset with lateral prongs. It is important to note 



