the echinoid fauna from japan and adjacent regions part i

172 S. NISIYAMA
the Miocene forms, may be regarded as an allopatric, and, in turn, the living form
has descended from the Miocene ancestor.
Genus Phyllacanthus BRANDT, 1835
Phyllacanthus BRANDT, 1835, p. 267 (in separate p. 67).-A. AGASSIZ, 1872-74, pp. 149, 388
(pro prate).-PoMEL, 1883, p. l11.-DuNCAN, 1889-a, p. 32.-MoRTENSEN, 1903-b, p. 30.­
DbDERLEIN, 1906, p. 103.-H. L. CLARK, 1907, p. 172.-H. L. CLARK, 1925, pp. 2, 9.­
MORTENSEl':, 1928-b, p. 500, text-figs. 160-162.-COOKE, 1941, p. 3.-H. L. CLARK, 1946, p.
281.-COOKE, 1959, p. 10.
Haplotype.-Cidarites (Phyllacanthus) dubia BRANDT, 1835, p. 268 (68) (Bonin Islands).­
Phyllacanthus dubius (BRANDT) A. AGASSIZ, 1872-74, pp. 150, 389, pI. If, figs. 6, 7.­
MORTENSEN, 1928-b, p. 510, pI. 55, fig. 1, pI. 56, figs. 1-2, pI. figs. 4-6, pI. 74. fig. 7, pI.
88, figs. 13-17, text-figs. 164-166 (Bonin Islands, littoral).
Leiocidaris DESOR, 1855-57 (56), p. 48.-DE LORIOL, 1873, p. 63.-POMEL, 1883, p. 111.-DuNCAl':,
1889-a, p. 31.-LAMBERT and THIERY, 1910, p. 153.
Logotype.-Cidarites imperialis LAMARCK, 1816, p. 54.-Phyllacanthus imperialis (LAMARCK)
A. AGASSIZ, 1872-74, pp. 151, 391, pI. 1, fig. 2.-MoRTENSEN, 1928-b, p. 504, pI. 54, fig. 4,
pI. 57, fig. 3, pI. 74, fig. 6, pI. 88, figs. 4-10, text-fig. 163 (Red Sea-Zanzibar-Ryukyu
Islands, in 0-73 metres depts). [DE LORIOL, 1873, p. 63J.
Test thick, with prominent, non-crenulate primary tubercles. Apical system
small, rarely exceeding 0.4 of horizontal diameter of test, very compact and closely
covered with tubercles (spines); dicyclic, oculars generally widely exsert ; madreporite
conspicuously larger than the other genital plates, encroaching upon the small anal
area. Scrobicular tubercles conspicuous, usually with a well limited elevation on the
side towards the areole. Ambulacra sinuate; the space inside the marginal tubercles
usually very narrow, filled up by small tubercles. Pores conjugate, but upper part
of wall somewhat raised. Peristome large, usually 0.4-0.5 of horizontal diameter of
test. Ambulacral series on peristome biseriate or pluriseriate. Primary spines thick
and stout, cylindrical or fusiform, with fine granules more or less distinctly serially
arranged, the surface otherwise covered by a spongy structure of branching outgrowths;
spines smooth, never prominent thorns. Secondary spines broad, fiat, closely
appressed, the minor ones more or less scale-like; at most some larger spines along
the inner edge of genital plates and around anal and genital openings, forming prominent
tufts. Both large and small globiferous pedicellariae without an end-tooth;
no limb on the stalk; tridentate pedicellariae with serrate, longitudinal crests in the
blade, basal part often thorny on outer side (after MORTENSEN, 1928-b).
The elimination of Prionocidaris baculosa (LAMARCK, 1816) and its allies, in which
the primary spines with more or less numerous projecting thorns or ridges, at least
near base, or with the spotted collar, leave this as a natural group of Ph. imperialis
(LAMARCK, 1816) and its allies, in which the primary spines are cylindrical or terete,
sometimes with longitudinal series of small serrations but never thorns or projecting
ridges or spotted collar, as are usually known in the large Indo-Pacific Cidarids.
This genus dates back at least to the Miocene, and rather widely distributed in the
Indo-Pacific Oceans.
The peculiar feature of the scrobicular tubercles and of the inner structure of
the primary spines, as has been pointed out by MORTENSEN (1928-b, pp. 501, 502)
seems to be rather unique among the Recent Cidarids. The scrobicular tubercles are