HOLASCELLA TARAXACUM. 35 



axes is to be noted, two rays of such hexactines lying in one axis, and the ray of 

 the pentactines which has no opposite being longer than the four rays lying in 

 the two other axes. The rays are straight, conic, pointed or blunt, 120-180 m 

 long and 3-8 ix thick at the base. With the exception of the base and the extreme 

 tip, which are smooth, the rays are covered with spines, 1-1.5 ^ long. The distal 

 spines are distinctly recurved (Plate 22, figs. 18, 19), the proximal ones arise 

 nearly vertically. 



The rare oxyhexasters (Plate 21, figs. 1, 2, 9} are about 95 m in diameter. 

 Their equal and regularly arranged main-rays are straight, fairly smooth, 19 ^ 

 long, 4 yu thick at the base, and slightly attenuated towards the distal end. Each 

 main-ray bears a terminal verticil of usually three end-rays, enclosing angles of 

 about 45° with the continuation of the main-ray. The end-rays are perfectly 

 straight, 37 /z long, 2 ^ thick at the base, conic, sharp-pointed, and covered with 

 minute spines. 



The rare onychhexasters (Plate 22, figs. 27, 28) are 98-105 n in diameter and 

 have a thickened centre, 4-5 ^ in diameter. The main-rays are regularly 

 arranged, in the same spicule faii'ly equal, straight, on the whole cylindi-ical, 

 8-11 n long and 1.5-2.3 ju thick. They bear from one to four, usually three, 

 end-rays, and sometimes also one or a few irregular knob-like protuberances 

 on their sides. The end-rays are 30-50 /u long and 0.6-1 ix thick at the base. 

 Distally they taper gradually to about 0.3 ix. The end-rays arise nearly verti- 

 cally from the main-ray and are cm-\-ed in an S-shaped manner, their proximal 

 part strongly concave towards the continuation of the main-ray, their distal 

 part sUghtly in the opposite direction. This curvature is different in different 

 end-rays and the degree of divergence of the chords of the end-rays from the 

 continuation of the main-ray is variable. Each end-ray bears several terminal 

 spines. These generally arise at nearly right angles, are curved, concave towards 

 the centre of the spicule, slender, and 2-5 m long. In view of the shape of the 

 end-rays these onychliexasters might also be termed cahcocomes. 



Of graphiocomes only a few centres (main-ray crosses) have been observed. 

 The main-rays are regularly arranged, equal, 11-13 m long and 2.5-4 ix thick. 



The abundant discohexasters (Plate 21, figs. 3-7, 10-13) are regularly spherical 

 and measm-e 180-290 ix in total diameter. Thek main-rays are regularly ar- 

 ranged, in the same spicule equal, perfectly smooth, about 14 ^ long, 3.5-5 ai 

 thick in the middle, and thickened at both ends ; proximally to the centre of the 

 spicule, distally to a stout, lens-shaped, transverse disc from the margin and 

 distal face of which the end-rays arise (Plate 21, fig. 10). The end-rays are 



