28 TROPICAL PACIFIC ECHINI. 
(Pl. 3°, fig. 6) have a comparatively smaller head and longer neck. The 
triphyllous pedicellarie (Pl. 3%, fig. 7) are slightly larger, and the globiferous 
pedicellarie (Pl. 3°, fig. 8) larger than those of P. pedifera. 
The tridentate pedicellarie of Colobocentrotus Mertensii (Pl. 3°, fig. 9) 
are closely allied to those of P. atrata, as are also the ophicephalous 
ones (Pl. 3%, fig. 12). The triphyllous pedicellariz (Pl. 37, fig. 10) have a 
proportionally shorter neck and larger head than in the two species named 
above. 
In the genus Podophora we find four kinds of pedicellarie: the ophi- 
cephalous, tridentate, triphyllous, and globiferous. On Pls. 4-6 I have given 
figures of the valves of the four kinds taken from different parts of tests of P. 
pedifera. Their position is noted in the description of the Plates. The 
figures will give a far better idea of the characteristics of the pedicellariz than 
any description I can give. Taking the figures of the valves of ophicephalous 
pedicellarie of P. pedifera (Pls. 4, figs. 1-6; 11-17; 6) one cannot 
fail to be struck with the asymmetry of the valves, the great variation in 
the size and arrangement of the foramina, in that of the hinges, of the serra- 
tions of the edges, to say nothing of the great variation in the size of the 
ophicephalous pedicellariz which vary from .33 mm. to .61 mm. in length ; we 
note such extremes in the shape and the ornamentation of the ophicephalous 
pedicellarie of P. pedifera as those of Pl. 6 figs. 1, 2, 4, 9, 10, 12, 14, 16, 17, 
taken from four individuals. 
The valves of the globiferous pedicellarie of the same species (Pls. 4, 
figs. 18-22; 5, figs. 10-13) taken from three specimens show equally great dif- 
ferences in shape, size, and ornamentation; they vary from .21 mm. to .37 mm. 
in length, and even of the triphyllous pedicellarix figured (Pl. 4, figs. 7-9) no 
two of the valves are alike. 
We finally come to the tridentate pedicellarie of P. pedifera (Pls. 4, 
figs. 7-10; 5, figs. 1-6) varying in length from .86 mm. to .99 mm. 
The figures are from pedicellarie taken from five specimens, and they 
speak for themselves. No two are alike, either in shape, size, outline, or 
ornamentation. 
The tridentate pedicellarie of P. atrata, figured on Pls. 18, figs. 
1-6, 13-16; 19, figs. 1-13, were taken from three specimens. The valves vary 
in length from .41 mm. to .90 mm. The blade of P. atrata is much more 
elongate than the blade of P. pedifera. The variation in the serration of the 
edge of the blade is very marked (compare Pl. 18, figs. 6, 15, 16 with the same 
