28 TKOPICAL PACIFIC ECHINI. 



(PL 3% fig. 6) have a comparatively smaller head and longer neck. The 

 triphyllous pedicellarice (PI. 3% fig. 7) are slightly larger, and the globiferous 

 pedicellarise (PI. 3% fig. 8) larger than those of P. 2:tedifera. 



The tridentate pedicellarise of Colohocentrotus Mertensii (PI. 3% fig. 9) 

 are closely allied to those of P. atrata, as are also the ophicephalous 

 /of ones (PI. 3% fig.-7*). The triphyllous pedicellarice (PI. 3% fig. iO^ have a /// 

 / proportionally shorter neck and larger head than in the two species named 

 above. 



In the genus Podophora we find four kinds of pedicellarise : the ophi- 

 cephalous, tridentate, triphyllous, and globiferous. On Pis. 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 pedicellarioe than 

 any description I can give. Taking the figures of the valves of ophicephalous 

 pedicellariae of P. jjedifera (Pis. 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 pedicellarias which vary from .33 mm. to .61 mm. in length ; we 

 note such extremes in the shape and the ornamentation of the ophicephalous 

 pedicellariae of P. pedifera as those of PI. 6 figs. 1, 2, U, 9, 10, 12, U, 16, 17, 

 taken from four individuals. 



The valves of the globiferous pedicellarice of the same species (Pis. 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 pedicellariaj figured (PI. 5, figs. 7-9) no 

 two of the valves are alike. 



We finally come to the tridentate pedicellarife of P. pedifera (Pis. 4, 

 figs. 1-10; 5, figs. 1-6) varying in length from .86 mm. to .99 mm. 

 The figures are from pedicellarioe taken from five specimens, and they 

 speak for themselves. No two are alike, either in shape, size, outline, or 

 ornamentation. 



The tridentate pedicellariae of P. atrata, figured on Pis. 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 PI. 18, figs. 6, 15, 16 with the same 



