322 THE VOYAGE OF H.M.S. CHALLENGER, 



then become spread over the entire plate in two lamellse. The beams of the framework 

 are more or less richly beset with pointed tubercles. The freely -projecting prongs or 

 conical pegs are further especially rough and tubercled, while in the interior of the 

 skeleton portions occur in which the beams appear almost or entirely smooth. 



The dermal skeleton consists of strong peutacts of variable size, and in these the 

 distal ray is entirely absent. The four cruciately disposed transverse rays are slightly 

 and uniformly bent inwards, and each terminates in a blunt point. While the outer 

 surface of these transverse rays is thickly beset with strong conical prickles, which 

 gradually decrease in height towards the lateral margin, the inner surface is quite smooth 

 (PI. LXXXVIII. fig. 3). The simple conical attenuated proximal ray varies in length, 

 and is, on the other hand, uniformly beset all round with a few simple conical prongs, 

 which stand out at right angles.^ In addition to the proximal radial ray of the pentacts, 

 scopulse extend towards the dermal membrane. These are to be reckoned among the 

 smaller types. The stalk always ends in a somewhat rough point, and exhibits close 

 beneath the forking an often sharply defined annular thickening. The four (more rarely 

 three or five) teeth are quite distinct from one another, and somewhat divergent. They 

 are either simply blunted or provided with an insignificant knob-like swelling. 



The gastral skeleton lying on the other side of the flat section exhibits the same 

 structure. Here also we find the same pentacts with a pronged upper surface, curved 

 transverse rays, and a conical radial ray. The scopulee are also similar to those of the 

 dermal surface (PL LXXXVIII. fig. 1).' 



Among the parenchymalia, in addition to the normal uncinates of variable length and 

 thickness, numerous small discohexasters occur with somewhat rough straight rays, which 

 may be slightly bent here and there, and bear terminally a small somewhat convex 

 marginally fringed transverse disc. By di\dsion of one, or a few, or all of the rays into 

 two or more (seldom more than four) terminal rays, discohexasters of various forms arise, 

 in which the terminal rays are about three times as long as the shaft from which they 

 spring (PI. LXXXVIII. figs. 8, 9). Between these discohexacts and discohexasters, 

 oxyhexacts and oxyhexasters of the same size, and on the whole of similar form, occur. 

 They also exhibit a similar roughened surface. 



The structure of the soft parts presents a general resemblance to that which we have 

 already seen in the Euretidaj, except that, in relation to the much greater thickness of 

 the wall, the aff"erent and eS"erent passages are longer and sometimes slightly ramified. 

 From the subdermal lacunae straight canals extend to near the subgastral spaces, and 

 between these afi"erent passages lie the efi"erent canals, which are also straight, and extend 

 from below the subdermal lacunae to the subgastral cavities into which they open widely. 



1 111 the figure (PI. LXXXVIII. fig. 3) the prickles of the radial ray are by mistake provided witli incurved, 

 instead of perpendicularly disposed prongs. 



^ By mistake, the gastral scopulte are omitted in the figure. 



