the echinoid fauna from japan and adjacent regions part i

The Echinoid Fauna from Japan and Adjacent Regions 189
391) in Hemicidaris intermedia and H. luciensis, it is proved beyond any doubt that
the Hemicidarids belong to the order of the Arbacioids. Accordingly, the Hemicidarids
have no nearer relation to the Diadematoids, but their relationship should
be to the Acrosaleniids, as well as to the Pseudodiadematids (they have also strongly
keeled teeth and the foramen of dental pyramid is open-MORTENSEN, 1932-c, p.
435, text-fig. 2.-1935, p. 423, pI. 73, fig. 1).
MORTENSEN (1935, p. 424) was strongly impressed by the great general resemblance
existing between some Hemicidarids and Pseudodiadematids in the dental
apparatus, but in recognizing the difference in the character of the spines; e.g., in
the former the spines are with an outer layer, whereas in the latter the spines are
without outer layer, he classified the Hemicidarids with the Pseudodiadematids in
his suborder Phymosomatina. His point is that the writer adopts the view, almost
unanimously profounded by BEURLEN, DURHAM and MELVILLE, that the Hemicidarids
are closely related to the Acrosaleniids, and should be classified together in suborder
Salenioina (Hemicidarina).
There is a single species of the genus Pseudocidaris in our collection.
Genus Pseudocidaris ETALLON, 1859
Pseudocidaris ETALLON, 1859-61 (59), p. 4.-DESOR and DE LORIOL, 1868-72 (69), p. 88.­
ZITTEL, 1879, p. 501.-COTTEAU, 1880-85 (80), p. 13.-PoMEL, 1883, p. 95.-DuNCAN, 1889a,
p. 51.-LAMBERT, 1900-a, p. 482.-LA:VIBERT and THIBRY, 1911, p. 167.-MoRTENsEN,
1935, p. 401, text-figs. 211-212.
Logotype.-Hemicidaris thurmanni AGASSIZ, 1840-a, p. 8.-Pseudocidaris thurmanlli (AGAS­
SIZ) COTTEAU, 1880-85 (80), p. 32, pI. 269, figs. 6-15, pI. 217, figs. 1-9 (Rauracian of
France). [LAMBERT and THIERY, 1911, p. 167J.
Test small to moderate in size, more or less swollen. Ambulacra narrow, rather
'strongly sinuate; ambulacral plates above th ambitus all simple primaries, each with
a smooth, imperforate tubercle, all equally developed; at and below the ambitus the
ambulacral tubercles are large, perforate, crenulate, as typical in Hemicidarids.
Apical system dicyclic; peristome large, with distinct gill-slits. Primary spines
short, thick, egg-shaped.
This Hemicidarid genus ranges from the Bathonian to the Cenomanian, and
distributed in Europe, North America, Central Asia, and India. Its primary spines
are large, massive, cylindrical and fusiform, or pear-shaped, usually striated longitudinally,
or rarely granular, and superficially resemble those of Balanocidaris, a
Cidarid.
This genus differs from its ally, Plesiocidaris POMEL, 1883, only in the character
-of the spines; i.e., in the latter the primary spines are long and cylindrical, but the
ambulacral structure is in common with each other with the simple primary plates
above the ambitus and only oligo porous compound plates at and below the ambitus;
it is regarded as the most primitive of the Hemicidarids.
Pseudocidaris simulans NISIY AMA, 1950
Pseudocidaris simulans NISIY AMA, 1950-a, p. 29, pI. 4, figs. 1-2.
Holotype.-IGPS colI. cat. no. 66504.