the echinoid fauna from japan and adjacent regions part i

188 S. NISIYAMA
rather deep, 5.5 mm wide and 4.5 mm high in a plate 7 mm wide and 5 mm high;
large scrobicular tubercles make a complete circle around the uppermost areoles,
they become continuous around; secondary tubercles form only a longitudinal series
to each side of areoles, particularly distinct along the adradial side; median space
of interambulacra at the ambitus covered with secondary tubercles, but the median
line distinct on the aboral surface.
Apical system large, but more or less affected by subsequent deformation, about
0.5 of horizontal diameter of the test; periproct pushed out to right, ocular (1) being
widely insert; suranal plate large, pentagonal in outline, about 5 mm long and wide,
and in contact with all five genital plates; oculo-genital plates seem to be rather
smooth, excepting a few small tubercles, generally 2 or 3 on the genital plates and
usually one on the ocular plates.
Peris.tome rather small, nearly as large as the apical system; gill-slits appear to
have been broad and deep.
Distinction.-This new species resembles Sal. deleaui COTTEAU (COTTEAU, 1889-
94 (92), p. 480, pI. 296, figs. 11-16) from the Eocene of France, but distinguished from
it by having much more numerous ambulacral and interambulacral plates in nearly
equal-sized specimens. This species is also superficially related to Salenidia blanfordi
(DUNCAN and SLADEN, 1882) (Salenia blanfordi DUNCAN and SLADEN, 1882-a, p. 29,
pI. 6, figs. 1-8), from the Ranikot Series (Eocene) of India, with respect to the
numerous coronal plates of the test, but differs from it in the structure of ambulacral
plates, and in the suture of the apical system.
Family HEMICIDARIDAE WRIGHT, 1857
Hemicidaridae WRIGHT, 1857-78 (57), p. 68.-DuNCAN, 1889-a, p. 48.-GREGORY, 1900-b, p.
307.-LAlvlBERT and THIERY, 1911, p. 167.-JAcKsoN, 1912, p. 202.-MoRTENSEN, 1935, p.
384.-BEURLEN, 1937-a, p. 41.-TERMIER and TERMIER, 1953, p. 896.
Test of usually moderate size, usually flattened below, often rather high.
Ambulacra with compound plates of the salenioid or diadematoid structure, and
large perforate, crenulate tubercles on the oral side, rather abruptly narrowing at
the ambitus; the plates being then simple primaries or indistinctly compound, with
tubercles much smaller than those at or below the ambitus. Each of the interambulacral
plates with a large, perforate, crenulate, only very exceptionally smooth,
tubercle; the surrounding large areoles usually broadly contiguous; sometimes the
primary tubercles reduced in size the upper part of interambulacrum. Apical system
simple, with no special development of the periproctal plates. Peristome usually
large, with conspicuous gill-slits. Primary spines of the Cidarid type, with a distinct
collar and an outer layer on the shaft; secondary spines flattened. Pedicellariae
and sphaeridia unknown (from MORTENSEN, 1935).
From the Lower Lias (Hettangian) to the Middle Cretaceous (Cenomanian).
Most of the former authors have regarded the Hemicidarids as related to the
Diadematoids; even such author as JACKSON (1912, p. 202) also classified them with
Diadematids.
(1935) on the
the foramen
However, after the more recent observations, made by MORTENSEN
dental character of the Hemicidarids, e.g., the teeth being keeled and
of dental pyramid open but rather deep (1935, text-figs. 206b-e on p.