KEPORT ON THE HEXACTINELLIDA. 197 



inferiorly. Owing to the insufficient preservation of the single specimen, it -was 

 imiJossible to determine wlietlier a Pali/thoa-crnst enveloped the basal tuft, below the 

 inferior extremity of the body. Below the superior terminal sieve-plate, there is a flat 

 hollow space, from which four cruciately arranged wide passages, furnished with lateral 

 and terminal diverticula and canalicular prolongations extend into the parenchyma. 

 Nearly up to the sieve-plate, the centre is occupied by a columella, ending freely 

 in a conical prominence. From this central pillar the four cruciately arranged septal 

 plates radiate outwards, separating the four gastral spaces from one another (PI. XXYII. 

 fig. 14). 



Of the external skin, as also of a delicate narrow cuflf-like fi'inge which surrounds the 

 sieve-plate and separates it from the skin, only a few pieces are preserved. 



The spicules supporting the parenchyma consist of simple, flat oxyhexacts of 

 medium size, which are usually radially disposed at right angles to the surface, and 

 distributed with general uniformity over the whole body. The six rays are all of equal 

 length, and are very gradually narrowed towards their somewhat conically pointed 

 extremities. Besides these, numerous simple smooth oxydiacts occur, partly isolated, 

 partly disposed in strands. These sometimes exhibit a central swelling, either in the 

 form of a simple ring, more or less sharply marked off", or in the form of four cruciate, or 

 more rarely of two opposite roundish protuberances. In these well-developed central 

 portions an axial-canal cross can usually be seen. Less abundantly than these diacts, 

 triacts occur, which generally exhibit two long rays, lying in one axis, and a much 

 shorter thii'd ray, at right angles to the former and springing from a slight median 

 swelling. 



Near the narrowed end of the body, and especially in the porous basal cushion, 

 hexacts, pentacts, tetracts, triacts and diacts occur, with cylindrical rays, which do not 

 run out to a point, but exhibit a truncated or even swollen end, and are terminally, and to 

 a greater or less distance inwards, thickly beset with conical tubercles. As an illustration 

 of the peculiarly modified spicules of the basal cushion, I have figured a triact on PL 

 XXVII. fig. 18. Tetracts are there, however, most abundant. 



I have here and there found such a simple regular form of small oxyhexact, with 

 delicate narrow rays, as is represented in PI. XXVII. fig. 20. Very frequently, on the 

 other hand, and throughout the whole parenchyma, such forms occur as are seen in 

 PI. XXVII. fig. 23. The long narrow rays, covered with small, not oblique but 

 directly transverse protuberances and peaks, are more or less markedly bent round in 

 their distal portions, and the bendings of the two rays which lie in the same axis are 

 always in the same plane, but in opposite directions. The planes of curvature of the 

 three axes of the spicule form with one another equal angles of 120°. The representation 

 of these hexacts with curved rays in PI. XXVII. fig; 23 is so far unsatisfactory, since one 

 cannot recognise in it that three rays are approached by their ends, and their three 



