HEXACTINELLA MONTICULARIS. 147 



disc, 1-2.5 n in transverse diameter (Plate 28, figs. 11, 20). Sometimes these 

 spines are so small that the end-rays appear terminally rounded and destitute 

 of terminal discs. 



The scopules (Plate 28, figs. 1-9, 13, 14) are 220-400 ^ long. They consist, 

 of a stout centrum, from one side of which arises a simple shaft, and from the 

 opposite a verticil of end-rays. Sometimes one or two end-rays are also attached 

 to the sides of the centrum. 



The centrum is 6.2-9.6 ^ broad, 4-9 m long, and has four lateral protulaer- 

 ances arranged regularly crossways. Wlien small these protuberances appear 

 as slight rounded elevations (Plate 28, figs. 7-9), when large as short, cylindrical, 

 terminally rounded ray-rudiments, equaling the shaft in thickness (Plate 28, 

 figs. 5, 6). The centrum and its protuberances are uniformly and densely 

 covered with minute spines. 



The shaft is 200-345 m long, straight or. rarely, curved. It is nearly 

 cylindrical for the greater part of its length, and rather abruptly attenuated to a 

 sharp point. It is 3-4.5 m thick at the base, where it rises from the centrum; 

 in the middle of its length it is slightly thinner, or, not so frequently, as thick or 

 slightly thicker than basally. The middle-part of the shaft is nearly smooth. 

 The proximal part, for a distance of about 30 n from the centrum, is, like the 

 centrum, densely covered with minute spines. In a belt which is 10-20 m broad 

 and situated a short distance from the distal end, larger, particularly broader 

 sparsely scattered spines occur. 



Of end-rays there are from five to nine, most frequently seven. As men- 

 tioned above, these generally aU rise from the apex of the centrum, that is the 

 face opposite the shaft. These terminal end-rays are slightly curved, concave 

 to the continuation of the axis of the shaft for a short distance, and, for the 

 remainder of their length, straight or curved slightly in the opposite direction 

 (outwards). They diverge above more or less and together form a stouter or 

 more slender, brush-like or calyculate verticil, 9-22 fi broad at the distal end. 

 These end-rays are 1 1-05 ju long, most frequently 1 1-30 ix. Of 33 measured : — 



inc; 



