LANUGONl'CHIA FLABELLUM. 



109 



Fig. 3. — Diiscohexasters. 



The large discohexaskrs measure 165-220 ju in total diameter. Their main- 

 rays, which are regularly arranged and enclose angles of 90° with their neigh- 

 bours, are 8-10 n long and 4.5-7 ^u thick. Each main-ray bears a terminal 

 verticil of usually four end-rays, which arise steeply from the main-rays, but at 

 once curve outwards, and are quite straight, apart from the short, curved, basal 

 part. The basal curvature is such that the distal straight and middle-parts of 

 all the end-rays become fairly concentric with the centre of the spicule, and also 

 fairly equidistant ; the whole discohexaster in consequence appearing as a quite 

 regular rosette. The end-rays are 90-105 fi long and 3.5-G fi thick at the base. 

 They are attenuated distally and are 1.5-3 m thick at their thinnest point, a 

 short distance below the end. From here they again thicken and measure, at 

 the end itself, 3-5 m in transverse diameter. Below the thinnest point the end- 

 rays bear minute backwardly directed spines. The spines are rather sparse at 

 the base of the ray but become very nimierous distally towards its thinnest point. 



