LANUGONYCHIA FLABELLUM. 
109 
The large discohexasters measure 165-220 n in total diameter. Their main- 
rays, which are regularly arranged and enclose angles of 90° with their neigh- 
bours, are 8-10 /i long and 4.5-7 n 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 m long and 3.5-6 /x 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 n 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 numerous distally towards its thinnest point. 
