130 
EURETE ERECTUM. 
times that the spines were arranged in elongate spiral rows ; in other cases no such 
spiral arrangement could be made out. Often the spines are restricted to the 
distal and lateral sides of the rays; sometimes, however, they are also found on 
the proximal side. 
The irregular gastral pinule-derivates (Plate 30 , fig. 3) are similar to the regu- 
lar pentactine-like ones and differ from them only in one or two of their lateral 
rays resembling the distal rays of pinules. 
The uncinates (Plate 31 , figs. 13, 14) are slightly curved or nearly straight, 
pointed at both ends, 0.5-1. 6 mm. long, and 4-9 m thick. Their spines are 7-27/x 
long, and 0.6-1 m thick at the base. They either diverge considerably (Plate 31, 
fig. 14) or are nearly parallel to the shaft (Plate 31 , fig. 13). Their tips are 1.5- 
4 m distant from the shaft. This elevation of their tips is by no means always in 
proportion to their length. 
The discohexasters (Plate 31 , figs. 15, 18, 21) measure 50-70 /j. in total 
diameter. Their main-rays are regular, smooth, straight, 6-10 n long, and 1.6- 
3 ,u thick. Each main-ray bears from one to four end-rays. These are usually 
curved, concave to the continuation of the main-ray at the base, and nearly 
straight farther on. They are 18-26 m long, 1.2-2 n thick at the base, and 
attenuated distally to 0.8-1. 5 The end-rays bear along their length minute 
recurved spines, and at the end a terminal verticil of similar but larger spines, 
which together form a kind of terminal disc with deeply serrated margin 2.5-4 /x 
in transverse diameter. 
It is possible that there are two kinds of discohexasters similar in size, but 
differing in respect to the end-rays, one with more slender and less spiny, the 
other with stouter and more spiny end-rays. Since, however, these asters are 
scarce I was unable to decide whether they all belong to the same series of forms, 
or whether two distinct varieties of them, as indicated above, should be distin- 
guished. 
The dermal scopules (Plate 31 , figs. 16b, 17, 19) are 200-420 n long and 
consist of a centrum 4-10 n long and 5.5-11.5 n broad, from which arises at one end 
(the inner) a simple shaft, and at the opposite (the outer) a bunch of end-rays. 
The centrum is not well-defined, often it passes quite gradually into the 
shaft. It and the proximal part of the shaft are densely covered with minute 
spines. The shaft is straight, cylindroconic, 170-330 ^ long, 3-6 n thick at the 
base, and pointed at the end. Sometimes, particularly in the dermal scopules 
with only two end-rays, this spinulation extends quite to the end of the shaft. 
Some of the dermal scopules have four end-rays, others only two, and a few have 
three. The dermal scopules with only two end-rays are fork-like. The end-rays 
