HEXACTINBLLIDA. 9 



each 83 x 11/a ; in C autogastral pentactins (IV. 3g^) are, in addition to the hexactins, 

 quite common. 



On re-examining the autogastral hexactins of A, B, C, I find the differences are not 

 so great as is depicted in IV. 2c and IV. 3c. The spicule shown in IV. 2c has excep- 

 tionally long and slender rays, and that shown in IV 3c has exceptionally short and blunt 

 rays. In specimen B the rays (266 x 15ja) are slender, sharp-pointed and slightly spined. 



Intermedia. The holoxyhexasters, hemioxyhexasters and monoxyhexasters show 

 a considerable amount of variation and abnormality, especially in the twin specimen C. 

 The holoxyhexasters and hemioxyhexasters are on an average from 100 to llO^u, in 

 diameter; fig. 3d shows a small holoxyhexaster (in optical section) only 62jU. in 

 diameter. Usually the primary rays are small but distinct. The monoxyhexasters 

 (IV. 3d^), 126ju, in diameter, have sharp-pointed secondary rays with rough surface, 

 are broad at the base and tapering to a sharp point. The abnormal spicules figured in 

 fig. 3d*' have the primary rays reduced to a central node or sphere, and the secondary 

 rays to a few spines. In some hexasters (IV. 3e) the secondary rays terminate in two 

 or three sharp prickles. 



3d' shows a stauractin-like monoxyhexaster, 145/x. in diameter, the rays having a 

 roughened surface. That these spicules are not young autodermal stauractins is shown 

 by the fact that the axial canals extend only a short distance from the centre. 



The calycocomes (IV. 3f-h), 80 to 90/a in diameter, show considerable variation, 

 not only in specimens B and C, but also in the same specimen, viz., variation in size, in 

 length and thickness of the primary rays, in the length and degree of divergence of the 

 secondary rays, and in the presence or absence of terminal disks. Fig. 3h, from 

 specimen B, is evidently abnormal ; here some of the secondary rays have fine bifid or 

 trifid terminations. 



Hemidiscohexasters of medium size (IV. 3e, e^), average about 85/a in diameter ; 

 the rays are sometimes thicker and straighter than is usual in this species. 



Monodiscohexasters, 90)a in diameter, occur rarely. Prof. Schulze figures 

 (6, pi. LV., fig. 8) a spicule of this kind — the only one found by him — from a 

 specimen from Kerguelen Island. 



The microdiscohexasters (IV. 3k), 50/x, in diameter, are mostly similar to those in 

 specimen A, with a narrow conical capitulum, whence two circles of secondary rays 

 originate; some, however, have a more disk-like capitulum (IV. 31); the secondary 

 rays in both kinds are extremely slender, being almost invisible under any object-glass 

 lower than y^ i^ch. Curiously enough, these rays are much more easily discernible in 

 the younger and less developed specimen A. 



All from W.Q., June 3rd, 1903. No. 10 hole ; 238 m. (130 fms.). 

 Other specimens have been found at : — 



Lat. 77^° S., long. 175° W. ; 548 m. (300 fms.) ; Sir J. C. Eoss's Expedition. 

 Prince Edward Island, 256 m. (140 fms.) ; Voy. 'Challenger.' 



