46 HOLASCELLA EUONYX. 
curved, conic spines, 7-15 » long. The basal part of these spines is directed 
outward, slightly upward, and usually encloses an angle of 105°-102° with the ray. 
Their ends are bent downwards, towards the centre of the spicule. These spines 
are regularly arranged and, when four in number, form a regular cross. 
The small discohexasters (Plate 24, figs. 10-12, 13b, 14b, 15-17; Plate 25, 
fig. 13a) measure 38-44 » in total diameter. They have a centrum 3.3-4 yu 
in diameter, from which six equal and regularly arranged main-rays arise. The 
main-rays are cylindrical, 6.5—9 » long, 1-1.4 » thick, and simply rounded off at 
the end. About 1 » below the end each main-ray bears a high frill, which appears 
as a round, subterminal, transverse disc 5-7 » in diameter. From the margin 
and the upper distal face of this dise very numerous diverging end-rays arise, 
which together form a short and broad bunch, at the distal end 19-25 u in diame- 
ter. The individual end-rays are, at the base, curved, concave to the continua- 
tion of the main-ray axis, and in their distal and middle-parts straight. They 
are 13 » long, throughout about 0.2 « thick, covered with exceedingly minute, 
recurved spines along their length, and crowned at the end with a verticil of 
similar but larger spines. These terminal spines together form a kind of end- 
dise, generally a little less than 1 » in transverse diameter. 
The large hemidiscohexasters and discohexactines are very similar and 
differ from each other only in that one of the main-rays bears two end-rays 
(Plate 25, figs. 2-5, 10, 11) in the former, whilst all six main-rays bear only 
one end-ray in the latter. The large discohexactines measure 173-232 u in 
total diameter, usually 194-215 u. Their six simple rays are fairly equal and 
regularly arranged, straight or slightly: and uniformly curved, and sometimes 
just perceptibly abruptly bent at the point where the short basal part, which is 
the main-ray, passes into the long distal part, which is the single end-ray. The 
short basal (main-ray) part of the ray contains an axial thread 6-7 u long; 
6-7 » is accordingly the length of the main-ray. The long distal (end-ray) 
part is destitute of an axial thread. The rays of the large discohexactines are 
95-110 » long and thickened at both ends. They measure at the base 4.5-6 u, 
at the thinnest point, which lies somewhere near the middle of their length, 
2.4—5 uw, and at the distal end 5-6.5 4 in transverse diameter. Along their 
length these rays are either quite smooth or bear a few minute, recurved spines. 
The end is crowned by a terminal verticil of usually five or six recurved spines, 
7-12 uw long, and 1.8-4 » thick at the base. These spines are conic, uniformly 
recurved and rather sharply pointed; together they form an exquisite anchor 
15-22 » broad and 10-16 yp high. 
