the echinoid fauna from japan and adjacent regions part i

264 S. NISIY Ai'vIA
subdivision of the family into two or three subfamilies, as stated by MOREENSEN
(1943-a, p. 288), seems to be superfluous.
This family of Japan and the adjacent regions is represented by the following
genera, viz., Echinostrephus A. AGASSIZ, 1863, Anthocidaris LUTKEN, 1864, Echinometra
(BREYNIUS) GRAY, 1825, Heterocentrotus BRANDT, 1835, and Colobocentrotus BRANDT,
1835; they are discriminated from one another as shown by the following key.
Key to the Japanese genera of the Echinometridae.
1. Ambitus circular; primary spines long and strong, usually simple ............ 2
Ambitus more or less elliptical; spines usually modified into heavy or flat-topped,
only exceptionally simple and normal .................................... 3
2. Test usually with ambitus above equator, or rarely not; only three or four porepairs
to the arc; a primary tubercle to each ambulacral plates; gill-slits
very shallow ................................................ Echinostrephus
Test generally with ambitus below equator; ambulacra polyporous, 7-8, or rarely
9 pore-pairs in an arc; distinctly petaloid on the oral side; spicules of tubefeet
bow-shaped (" biacerate "), with pointed ends ............ Anthocidaris
3. Long axis of test through A. I-LA. 3; marginal spines not forming a lateral
fringe or otherwise specially developed; ambulacra with 4-10 pore-pairs to
each arc; buccal plates with small spines ...................... Echinometra
Long axis through A. II (a)-I. A. 4 (a) ........................................ 4
Long axis through A. IV (b)-I. A. I (b) ........................................ 5
4. Primary spines very strongly developed, long, thick, heavy and pencil-like; pri-
. mary tubercles very large; ambulacra with 9-19 pore-pairs in an arc ..... .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Heterocentrotus
5. Aboral spines flattened, thick and very short, forming like a dense mosaic; primary
tuberclts moderate, in mid-zone 10-12 in two horizontal rows on each
interambulacral plate ...................................... Colobocentrotus.
There are fossil representatives of the genera Echinostrephus and Echinometra
in our collection.
Genus Echinostrephusll A. AGASSIZ, 1863
Echinostrephus A. AGASSIZ, 1863, p. 20.-A. AGASSIZ, 1872-74, pp. 119, 457.-BELL, 1881-a, p.
433.-POMEL, 1883, p. 78.-DuNCAN, 1889-a, p. 123.-MoRTENsEN, 1903-b, p. 139.-MEIS­
SNER, 1904, p. 1376.-H. L. CLARK, 1912-b, p. 342.-LAi'vIBERT and THIERY, 1914, p. 254.­
H. L. CLARK, 1925, p. 130.-MoRTENsEN, 1943-a, p. 304.-H. L. CLARK, 1946, p. 327.
Haplotype.-Echinostrephus aciculatus A. AGASSIZ, 1863, p. 20 (Sandwich Islands).-A.
AGASSIZ, 1872-74, p. 457, pI. 5a, figs. 10-12, pI. 6, fig. 20.
Raphidechinus LAMBERT and THIERY, 1914, p. 241.
Orthotype.-Echinus molaris BLAINVILLE, 1825, p. 88.-DE LORIOL, 1883-a, p. 31, pI. 4, figs.
2-2c (Indian Ocean).
Small forms of generally unusual shape of test, or rarely usual shape; the
greatest diameter is generally above the midzone (equator) ; aboral side usually flat;
circumference of test often pentagonal. Ambulacra with trigeminate plates (molare),
1) arpe90S = (J'rsprpos, cos, rO, is neuter gender, not masculine.