179 
it is very well possible, if one cares to take the trouble, to ident- 
ify them with accuracy. 
The present species is closely related to the Japanese species 
P. pellucida Doderlein. The main distinguishing characters are these: 
In P. pellucida the oral side is not regularly concave; there is a 
distinet bulging of the test a little distance from the mouth, espec- 
ially distinet in the posterior interradius, between the mouth and 
the anal area; the somewhat sunken posterior ambulacra serve to 
emphasize the bulging of the anal plastron. Outside the bulging 
the test is quite flat. This characteristic shape of the oral side 
serves very v/ell to distinguish P. pellucida from P. hinemoæ . 
Further the shape of the petals is somewhat different; in pellucida 
they are the widest in their inner part, the narrowing beginning rather 
abruptly at about the middle; in P. hinemoæ they are the widest about 
in the middle, then very gradually narrowing outwards. The gen¬ 
ital pores are doser together in P. hinemoæ than in P. pellucida. 
The test, upon the whole, is more coarse in P. hinemoæ than in 
the Japanese species. In regard to spines and pedicellariæ the only 
notable difference appears to be that the larger form of tridentate 
pedicellariæ is not found (at least in the material available) in the 
New Zealand species. Finally, the Japanese species is not known 
to occur outside the Japanese seas. 
15. Laganum depvessum Less. (?) 1 ). 
PI. VI, Fig. 32. 
Laganum depressum. L. Agassiz. 1841. Monogr. Scutelles. p. 110. Tab. 
23. fig. 1—7. 
— A. Agassiz. 1872. Revision of the Echini. p. 138, 
518. PI. XIII. f. Figs. 5-8. 
— De Meijere. 1904. Siboga-Echinoidea. p. 114. 
Taf. VI. Fig. 57; Taf. XVIII, Fig. 317—318. 
— H. L. Clark. 1914. Hawaiian a. o. Pacific Echini. 
Clypeastridæ etc. Mem. Mus. Comp. Zool. XLVI- 
p. 45. PI. 124. Figs. 7—12. 
') I have accepted H. L. C 1 a r k’s distinetion of the genera Laganum and 
Peronella , the former comprising the species having 5 genital pores, the 
latter those with only 4. This may not be in full accordance with the 
true interrelations of the different forms, but for the present this dis¬ 
tinetion is the most convenient. 
12 * 
