138 
EURETE SPINOSUM. 
29, fig. 10). In the few hemioxyhexasters, however, in which the main-rays are 
unequal, a corresponding irregularity is also observed in the end-rays (Plate 29, 
fig. 12). The regularly disposed end-rays are conic, sharp-pointed, and covered 
with minute, backwardly directed spines (Plate 29, fig. 14). In a few hemioxy- 
hexasters with exceptionally thick lateral main-rays the regularly disposed end- 
rays are reduced in length and terminally rounded. In the normal, regular 
hemioxyhexasters the end-rays are 25-44 n long, and 1.8-3. 7 ^ thick at the base. 
In the irregular forms the shortest are sometimes only 13 n long. The central 
end-ray of each group of three is straight throughout; the two lateral ones are 
either also straight throughout (Plate 29, fig. 12) or, much more frequently, 
straight only in their middle- and end-parts, but curved at the base, concave to 
the central end-ray. The chords of the lateral end-rays enclose angles of 47-52° 
with the central end-ray. 
Besides these regularly disposed end-rays other end- or branch-rays some- 
times arise from the lateral main-rays. Occasionally one or two supernumerary 
end-rays are added to the regularly disposed three. These additional end-rays 
extend, like the latter, in the plane of the lateral main-rays. More frequently a 
branch-ray is seen arising some distance below the end of the lateral main-rays. 
These branch-rays extend more or less vertically to the plane of the lateral 
main-rays, and are parallel to the apical rays. In size and spinulation the 
supernumerary end- and branch-rays are similar to the regularly disposed end- 
rays; they are, however, more frequently irregularly curved. 
The axis of each lateral main-ray is occupied by an axial thread (Plate 29, 
figs. 14-17, 19). This terminates at the end of the main-ray and does not send 
branches into the end-rays. The latter are destitute of axial threads. 
The scopuies (Plate 29, figs. 1-8, 26a) are 140-288 m long. They consist of a 
centrum, 3.8-7 n in diameter, usually 4-5 m, from one side of which arises a shaft, 
and from the other arise four or, rarely, five or six end-rays. The shaft is conic, 
straight, or slightly curved, 115-261 m long, and 1. 9-2.4 /x thick at the base. 
Near the distal end and often also near the base it bears minute spines. The end- 
rays diverge distally and together form a brush-like verticil 9-18 // broad at the 
end. The individual end-rays are very slightly curved, concave to the continua- 
tion of the shaft at the base, and nearly straight in their remaining part. They 
are 20-44 n long, 0.9-1. 5 m thick at the base, very slightly attenuated towards the 
end, and densely covered with minute, backwardly directed spines. At the end 
they bear a verticil of larger, recurved spines, which together form a kind of 
terminal disc with strongly serrated margin (Plate 29, figs. 7, 8). 
