the echinoid fauna from japan and adjacent regions part i

The Echinoid Fauna from Japan and Adjacent Regions 249
inclined and curved than in those of Ps. depressus. It may be an ancestral form of
the Recent species, Ps. depressus, as the adult form of this resembles some young
stages of the Recent form.
Suborder ECHINOINA CLAUS, 1876
Echinideae CLAU, 1876, p. 356.-Echinina MORTE;'\SEN, 1942, p. 225 (non Echinina GREGORY,
1900-b, p. 311).-MoRTENSEN, 1943-a, p. l.-TERYIlER and TERlvIIER, 1953, p. 909.­
NISIYAlvIA, 1954, p. 327 (in Japanese).-Echinoida CLAUS: DCRHA\I and MELILLE, 1957, p.
255 (order).
Type-family.-Echinidae GRAY, 1825.
Regular Echinoids with camarodont type of lantern, and with compound ambulacra
of the echinoid structure or its complex type. Test not sculptured. Tubercles
imperforate, smooth. Gill-slits neither sharp nor deep. Spines with solid axis,
without cortex layer.
From the Eocene to Recent.
The forms with circular ambital margin of this suborder. in general, resembles
the forms of the suborder Temnopleuroina without sculptures on the test; but, the
former are distinguished from the latter by both the indistinct and shallower gillslits,
and the character of the globiferous pedicellariae.
This suborder comprises a large number of Recent forms, in which four families
are divisible, e. g., the Echinidae, Strongylocentrotidae, Parasaleniidae, and the Echinometridae.
These families are distinguished from one another, according to MOR­
TENSEN, mainly by the structure of their globiferous pedicellariae.
There are fossil representatives of the families of the Strongylocentrotids, Para­
'saleniids, and the Echinometrids, in our collection.
Family STRONGYLOCENTROTIDAE GREGORY, 1900
Strongylocentrotidae GREGORY, 1900-b, p. 313 (pro parte).-MoRTENSEN, 1903-b, p. 137.­
DELAGE and HEROUARD, 1903, p. 245.-JACKSON, 1912, pp. 204, 216 (pro parte).-H. L.
CLARK, 1912-b, p. 340 (pro parte).-H. L. CLARK, 1925, p. l30 (pro parte).-MoRTENSEN,
1927-b, p. 312.-GRANT and HERTLEIN, 1938, p. 28 (pro parte).-MoRTE='iSEN, 1943-a, p.
183.-H. L. CLARK, 1946, p. 327 (pro parte).-TERyIlER and TER\IIER, 1953, p. 910.
Type-genus.-Strongylocentrotus BRA:\DT, 1835.
Test regularly hemispherical, of moderate to very large size. Ambulacra polyporous
of the complexity of the echinoid structure, apart from the adoralmost plates;
pore-zones not widened adorally. Tubercles imperforate, non-crenulate, regularly
·developed in both areas; no sculpture on the test. Apical system is usually with
·oculars (1) and (V) broadly insert. Buccal membrane with a varying number of
plates distally to the buccal plates, the larger ones carrying pedicellariae. Gill-slits
shallow, neither deep nor sharp. Spines generally short, simple, only exceptionally
about as long as the diameter of test. Globiferous pedicellariae very characteristic
in having a well developed neck, provided with circular and longitudinal muscles;
the stalk is hollow; the valves without lateral teeth. Spicules of tube-feet and
globiferous pedicellariae C-shaped with distal prominences, or simply bihamate. The
larva in its first stage does not form a basket structure; the fully formed larva has
no posterior transverse rod, but is provided with ciliated epaulets (from MORTENSEN,