ECHINONEUS CYCLOSTOMUS. 55 
actinostome from a spetimen 28 mm. long, which has the edge of its long neck 
bent inward like a collar, and which in turn contrasts to figs. 9-17, Pl. 23. The 
first one from a specimen measuring 11 mm. in length, and the two latter from 
one 20 mm. long. In a young specimen of 4 mm., the valve B (fig. 1), from the | 
anal system, and (fig. 2), from the right posterior ambulacrum, near the actino- 
stome, already have a difference in their shape. 
It should be noted that tridentate pedicellariae (figs. 17—26) were owing to 
insufficient space on the preceding plates placed on Pl. 22. The specimens were 
from the Paumotu Islands, South Pacific, and from the West Indies, and the 
figures readily show their diversity in shape. 
The ophicephalous pedicellariae are the most numerous, especially on the 
abactinal side, and they vary the least in form. Three valves, same pedi- 
cellaria (Pl. 21, figs. 3, 4, 6), from the left posterior interambulacrum, of the 
actinal side of the ambitus, from a specimen 34 mm. long, from Lord Howe 
Island can be regarded as typical; but a large number deviate as will be seen 
in valve C (fig. 7), and valve A (fig. 8), from the actinal side of the ambitus in 
the right posterior interambulacrum, and especially in valve A, with its long 
slender neck and articular loop pointed at the lower end. Of course a difference 
in shape is to be expected between pedicellariae from the abactinal side of the 
test, or near and on the apex, and those from the actinal side. This is shown 
in two valves, B (fig. 9), and C (fig. 10), of the same pedicellaria, from near 
the apical system of a 30 mm. specimen when compared with the figures referred 
to above. In valve B which is practically of the same height as that shown in 
fig. 4, the blade with a broad apophysis passes into the base almost without any 
neck; the articular loop is stout and sharp pointed at its lower end; the articular 
teeth are wide, and the articulation surface slopes to the left where the loop is 
thickest; this is reversed in the other (fig. 4), where it slopes to the right; this 
reversal is a common occurrence. Two valves, B and GC, in height 0.16 mm., 
from the apical system, of a specimen 11 mm. long, from Fakarava Island 
(PI. 21, figs. 17, 12), do not present any great deviation from two others, B and C, 
0.21 mm. in height from the actinal side of a specimen 15 mm. long, from 
Makemo Island, (figs. 13, 14). 
Of three valves, the same pedicellaria from the right posterior ambulacrum, 
near the anal system, from a specimen 30 mm. long, from Barbados (Pl. 21, 
figs. 15, 17), the blade has lost its discoidal form, and passes into the base almost 
without any neck. The loop is that of an ophicephalous pedicellaria, but the 
base and blade are exactly those of a tridentate form, and this may be noted 
even in valves (figs. 18—20), from the abactinal side up to the apical system. 
