296 HYAL0XE:\IA (PRIONEMA) fimbriatum. 



and distal spines are short, the middle ones have a maximum length of 15-28 /u. 

 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 m- 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 ^ long, on an average (of 42 measurements) 28.3 m- 

 They bear, along their whole length, with the exception of base and tip, rather 

 sparse conspicuous spines about 2 tx 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 ^ 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 n long, exceptionally as much 

 as 138 ft, on an average (of 29 measurements) 103.6 ^ long, 3-6.5 m thick at the 

 base, and thickened in the middle, where it measures 4-8 ix 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 ju 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 /i 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 jLi long. The maximum transverse diameter of the apical (distal) ray, 

 together with the spines, of these pinules (pinule-derivates) is only 7-9 ^. 



The pentactine megascleres underlying the superficial membrane (Plate 63, 

 fig. 7-9) have straight or only very slightly curved, usually conic rays, 13-60 ^ 

 thick at the base. Occasionally a ray is reduced in length and terminally 



