42 
HOLASCELLA ANCORATA. 
in total diameter. They generally have only one, sometimes two, very rarely 
three end-rays. Most of them are microdiscohexact.ines with one end-ray on 
each main-ray; some hemidiscohexactines with one end-ray on some main-rays 
and with two end-rays on others. A few are true discohexasters with two end- 
rays on all or with two end-rays on some and three end-rays on the other main- 
rays. The main-rays are regularly arranged and, in the same spicule, fairly 
equal. They are smooth, about 5 m long and 2.5-3. 7 n thick. The end-rays are 
straight or slightly irregularly curved, 50-110 n long, thinnest some distance 
below the distal extremity, and thickened at both ends. The proximal end is 
2-3 m thick, the thinnest point 0.7-1. 5 m, and the distal end 2.6-4 n- The end- 
rays bear very minute spines on their sides and a verticil of large, anchor-teeth 
like, strongly recurved spines at their end. These terminal spines are conic, 
8-10 n long and 1.2-1. 6 m thick at the base. They are not joined at the base 
to a terminal tyle or disc, and together form an exquisite anchor, 9-12 n broad 
and about as high. When two or three end-rays arise from a main-ray, they are 
usually arranged somewhat irregularly and enclose angles of 20°-45° with the 
continuation of the main-ray. When, as is the rule, there is only a single end- 
ray, it lies in the continuation of the main-ray, and usually passes into it so 
gradually that main- and end-ray together appear as a simple hexactine ray. 
Such simple rays are 65-115 /x long. 
Axial threads are found only in the main-rays. They appear as thin, fairly 
straight rods, are about 5 /x long, and terminate abruptly at the point where the 
main-ray divides into the two or three end-rays (Plate 23 , fig. 7, right), or passes 
into the single end-ray (Plate 23 , figs. 6, 7, left, upper and lower). The simple 
rays with only one end-ray consequently possess an axial thread only in their 
basal (main-ray) part. 
The few main-ray crosses observed, which may be centres of graphiocomes, 
consist of regularly arranged, equal, straight main-rays 10 n long and 3.5 m thick, 
from the ends of which large numbers of end-rays arise. 
The floricomes (Plate 24 , figs. 4-7) measure 48-60 m in total diameter. 
Their main-rays are regularly arranged, in the same spicule equal, cylindrical, 
straight, 6-7 /u long, and about 1.5 /x thick. Each main-ray bears a verticil of 
about twelve end-rays. All the end-rays arise at exactly the same level, 1-1.5 /x 
below the distal end of the main-ray, which protrudes for that distance in the 
shape of a rounded knob beyond the ring-shaped line of their insertion. The 
end-rays of the same verticil are exactly equal in size, shape, and position, rela- 
tive to the main-ray from which they arise. They are, measured along their 
