272 I. IJTMA : HEXACTINELLIDA. I. 



relatively very short (not over 2 ram. in length) and is some- 

 times represented merely hy a rounded boss. It enter.s into the 

 suj^port of the cuff. 



Of the cruciate, paratangential axes, the one in longitudinal 

 direction is the longest, reaching up to 30 ram. in length. The 

 superior ray in this axis, i. e., tlie ray which goes into the com- 

 position of each of the radial sieve-plate beams, is in length about 

 equal to or shorter than the inferior ray which is imbedded in 

 the parenchyma of the lateral wall. The lateral I'ays in the 

 transverse axis are always much shorter than either the superior 

 or the inferior ray ; sometimes they are as short as the distal 

 unpaired ray. Thickness of the r;iys at base 250-475 ii. The 

 superior and the infeiior rays commonly thicken somewhat at 

 a short distance from the central node, then gradually narrow 

 again toward the finely pointed end. 



The lateral rays, lying along the base of the cuff, run in 

 association with just the same diactin elements as compose the 

 parenchymal bundles of the lateral wall. 



The superior ray is distinguished from all the rest by 

 having a number of obsolete micro tubercles widely and sparing- 

 ly distributed over its surface (PI. XI, fig. 7). The microtubercles 

 are frequently only indicated. They disappear entirely to- 

 wards either end of the ray. Along with the ray in question 

 are found in a bundle bow-like oxydiactin-principalia and 

 diactin-comitalia, to complete the parenchymalia of the sieve-plate 

 (PL XI, fig. 8). Among the comitalia are not uncommonly 

 found small and slender-rayed hexactins, which pass over into 

 the shorter diactin-comitalia bv a gradational series of inter- 

 mediate forms. 



In the Challenger Eeport F. E. Schulze gave large oxy- 



