CAULOPHACUS SCHULZEI. 61 



measure 44-312 n in total diameter. The main-rays and end-ray verticils or 

 bunches of the same spicule are equal. Exceptionally (Plate 10, fig. 17) one 

 or two end-rays arise from a main-ray below the terminal verticil or bunch. 

 In one discocome one of the main-rays bore a stout branch, which was crowned, 

 like a main-ray, by a bunch of end-rays. In respect to these irregularities the 

 rays of the same spicule are unequal. The main-rays are straight, 20-65 ^ 

 long, cylindrical, and 1.5-7 yu thick. At their distal end they are abruptly thick- 

 ened to an inverted cone or convex disc, 7-16 ^ in diameter, from the distal 

 face of which the end-rays arise. The main-rays are generally perfectly smooth, 

 exceptionally they bear a few rather large spines. The axial thread of the 

 main-ray ends abruptly in the terminal thickening and does not give off branches 

 for the end-rays; the latter appear to be destitute of axial threads. The number 

 of end-rays on each main-ray is from six to eighteen or more. When their num- 

 ber is great, it is exceedingly difficult to count them. When few in number 

 they form a verticil, when more numerous, a bunch or brush, in which they are 

 fairly equidistant. The terminal verticils or bunches formed by the end-rays 

 appear as inverted cones with apical angles of 25-100°. The individual end-rays 

 are straight or curved in an S-shaped manner with outwardly directed distal end. 

 Measured along their chord they are 18-103 fi long. They are 2-3 n thick at 

 the base and taper gradually to 1-1.5 yu at the distal end. They are densely 

 covered with lateral spines all along their length, and crowned by a verticil of 

 terminal spines at the end (Plate 10, figs. 20, 21, 26). The largest spines are the 

 terminal ones. The verticil formed by them somewhat resembles a convex 

 end-disc with serrated margin and has in transverse diameter a maximum of 

 4.5 M- The lateral spines usually decrease in size very considerably towards 

 the proximal end of the end-ray, but in some of these spicules the proximal end- 

 ray spines are quite large (Plate 10, figs. 15, 16). All the spines arise obliquely, 

 their basal parts being inclined towards the centre of the spicule; their ends are 

 bent down in the same direction. They, therefore, appear strongly recurved 

 (Plate 10, figs. 15, 16). All the spines on the end-rays of the large discocomes 

 and the distal spines on the end-rays of all but the very smallest discocomes are 

 clearly visible. The spines on the proximal parts of the end-rays of the smaller 

 discocomes and all the spines of the smallest are, however, too minute to be 

 clearly discernible as such; the presence of these spines is indicated only by 

 (he rough appearance of the end-rays. 



The individual discocomes differ very considerably in size. A cursory 

 examination shows that the relative dimensions of the main- and end-rays, and 



