ECHINONEUS CYCLOSTOMUS. 53 
THe PEDICELLARIAE. 
Plates 18-23; Plate 26, figs. 16-19, 30, 31; Plate 27, figs. 12, 13, 23, 24, 35, 36, 43, 44. 
How great the variation of shape can be in pedicellariae of the same kind, 
taken from the same specimen, but from different parts of the test, is shown in 
the illustrations (Pls. 18-23) which are few when compared with the material 
available. To distinguish which valve of the three in any one pedicellaria is 
meant, since they are not of equal height, or the same form of loop, I have used 
in addition to Mortensen’s comprehensive terminology, the letters A, B, C; A, 
denoting the highest, C, the lowest, and B the intermediate valve. 
The tridentate pedicellariae are few in number, and found only on the 
actinal side of the test, near or a short distance from the oral and anal systems. 
Of three valves from the same pedicellaria (Pl. 18, figs. 1-6), from a specimen 
34 mm. long, from Lord Howe Island, no two of them have outlines exactly 
alike. The blade in valve A (fig. 2), at the upper part is ellipsoidal, and does 
not correspond to valve B (fig. 3), where it is circular; while in valve C (fig. 5), 
it is slightly pointed. We find the same irregularity in the base, which either 
slopes, or has a sharp prolongation on the right or left side close to the neck. 
A valve of another pedicellaria (Pl. 18, figs. 70, 11), has no indication of the 
articular loop, and the blade is possibly broken. Presumably it is a young 
tridentate pedicellaria. 
For uniformity one of the series valve B, was chosen for comparison. Three 
such valves (Pl. 18, figs. 7, 9), from a specimen 15 mm. long from Makemo 
Island, were taken respectively from near the actinostome in the odd posterior 
interambulacrum, from the odd anterior ambulacrum, and from the right ante- 
rior interambulacrum. The obvious difference in the form of the blades, which 
vary from a triangular point to a round top, in the variation in number of lateral 
teeth from 11 to 15 in each blade, and in the shape of the neck and bases, is most 
striking. They are very unlike those on PI. 20, figs. 8, 10-13, also from Makemo 
Island specimens. I find no specific identity between two valves (PI. 20, 
figs. 8 and /0), from the same specimen, 10 mm. long; one valve from the aboral 
end of the anal system, the other from midway between the actinostome and the 
ambitus, in the right posterior interambulacrum. In one of these the blade and 
base are of nearly the same height, while in the other the outline of the base is 
rounded, the long neck abruptly narrowed, and the blade short with indications 
of lateral teeth. In valve C (fig. 11), from another specimen 11 mm. long, 
these lateral teeth are very conspicuous. The same striking difference is observ- 
