296 
HYALONEMA (PRIONEMA) FIMBRIATUM. 
and distal spines are short, the middle ones have a maximum length of 15-28 n- 
These long spines point obliquely upwards and usually enclose an angle of 30°- 
40° with the axis of the distal ray. The maximum diameter of the distal ray, 
together with the spines, is 27-45 /x . The spines are conic, sharp-pointed, and 
straight or curved, concave towards the tip of the ray. They are usually simple, 
but occasionally bear small secondary spinelets. The lateral rays (Plate 62 , 
figs. 16-18) are straight, nearly cylindrical in their basal and middle-parts, 
abruptly pointed, and 23-36 m long, on an average (of 42 measurements) 28.3 /x. 
They bear, along their whole length, with the exception of base and tip, rather 
sparse conspicuous spines about 2 ^ long. The proximal spines are vertical, 
the distal ones inclined towards the tip of the ray. 
Among these pinules I found an abnormal one with a reduced distal ray 
only 20 n long, bent and rounded at the end, and destitute of large spines. 
The canalar pinules (Plate 62 , figs. 19, 32-41) are also nearly always pentac- 
tine. I found only a single hexactine one among them. This had a proximal 
ray 53 m long. The distal ray is straight, 80-122 ^ long, exceptionally as much 
as 138 n, on an average (of 29 measurements) 103.6 n long, 3-6.5 /x thick at the 
base, and thickened in the middle, where it measures 4-8 /x in transverse diameter. 
Its end appears as a slender, sharp-pointed cone. The distal ray bears irregu- 
larly arranged spines. The number of these spines is never great. Sometimes 
there are only three or four (Plate 62 , figs. 32, 41). The largest spines generally 
arise from the middle-part of the ray; proximally and distally they become 
smaller. The spines are conic, sharp-pointed, straight or curved, usually concave 
towards the tip of the ray. They are generally simple, only very rarely they 
bear small secondary spinelets. The large spines of the middle-part of the ray 
are usually 10-52 ^ long, strongly divergent and generally inclined towards the 
tip of the ray. Occasionally, however, some of them are vertical (Plate 62 , 
fig. 38) or inclined towards its base (Plate 62 , fig. 41). The maximum diameter 
of the distal ray, together with the spines, is 20-77 /x. The lateral rays are 
conic, 40-88 m long, and bear numerous small spines. 
These spicules are connected with the micropentactines described below 
by transitional forms, in which the spines of the distal ray are much smaller, 
only 1-3 m long. The maximum transverse diameter of the apical (distal) ray, 
together with the spines, of these pinules (pinule-derivates) is only 7-9 n. 
The pentactine megascleres underlying the superficial membrane (Plate 63 , 
fig. 7-9) have straight or only very slightly curved, usually conic rays, 13-60 /x 
thick at the base. Occasionally a ray is reduced in length and terminally 
