the echinoid fauna from japan and adjacent regions part i

The Echinoid Fauna from Japan and Adjacent Regions 263
characteristic of the ambulacra, form of test, and the tuberculation on coronal plates,
particularly of the ambulacral primary tubercles.
This species closely resembles Par. gratiosa A. AGASSIZ, 1863 (loc. cit), a Recent
species from the Indo-Pacific Oceans; but is distinguishable from the latter by the
narrower poriferous zones, and by the larger primary tubercles on ambulacra. The
difference of two species is clearly recognized when the specimen of this species is
directly compared with the young specimens (12-25 mm in longer axis) of Par.
gratiosa from Palao Islands, Micronesia. It seems evident that this species has
certain affinities with Recent species of the Indo-West Pacific, but not with the
Miocene Par. prisca (COTTEAU, 1875) (loc. cit.) of the West Indies, as suggested by
COOKE (1957, p. 361).
Family ECJ-IINOMETRIDAE GRAY, 1855
Echinometradae GRAY, 1855, p. 37.-Echinometridae GRAY: A. AGASSIZ, 1872-74, p. 423 (pro
parte).-BELL, 1881-a, p. 410.-PO:\IEL, 1883, p. 77.-DuNCAN, 1889-a, p. 115.-GREGORY,
1900-b, p. 313 (pro parte).-MoRTENSEI', 1903-b, p. 138.-DELAGE and HEROUARD, 1903,
p. 246.-MEISSNER, 1904, p. 1375.-JACKSOX, 1912, pp. 146, 204, 267.-H. L. CLARK, 1912-b,
p. 365.-H. L. CLARK, 1925, p. 141 (pro parte).-GIGXOUX, 1933, p. 121.-GRANT and HERT­
LEIN, 1938, p. 39.-MoRTENSEN, 1943-a, p. 277.-H. L. CLARK, 1946, p. 330 (pro parte).­
TERMIER and TERMIER, 1953, p. 910.
Type-genus.-Echinometra (BREYNIUS) GRAY, 1825
Test of small to very large size, varying in shape from round to elliptical, being
transversely elongate. Ambulacra with trigeminate to multigeminate (polyporous)
plates of the echinoid structure, or its complex type; pore-zones often petaloid,
widened adorally. No pits or sculpture in coronal plates aborally. Primary tubercles
imperforate, non-crenulate. Apical system usually with oculars 0) and (V) broadly
insert; suranal plate usually indistinct. Buccal membrane usually with scattered
plates, which carry number of pedicellariae, sometimes spines also; at least the
membrane contains a varying number of delicate plates imbedded in the skin. Primary
spines mostly long and strong, sometimes particularly long and thick, pencillike
(Heterocentrotus), or flattened, shield-like (Colobocentrotus). Pedicellariae, of the
usual four kinds; globiferous pedieellariae mostly without neck, with double poison
glands, and with compact stalk. Valves of globiferous pedicellariae with a single,
unpaired lateral tooth. Spicules usually of the simple bihamate type, but sometimes
with branched ends, or biacerate, with pointed ends (Anthocidaris), or coarse, triradiate
(Echinometra mathaei oblonga). In the first larval stage, the body skeleton
forms a complicate basket structure, the recurrent rod being double; in the second
fully formed stage, the larva has a well developed posterior transverse rod (after
MORTENSEN, 1943-a).
From the Miocene to Recent.
This is a rather well marked tropical family of some 10 genera, which are characterized
by their high specialization of the ambulacral structure and spines. As no
fossil genera are known which can be referred to this family, it might be in the
Recent Epoch that these specialized forms have had their main development. About
the source from which this highly specialized family of the Echinometrids have
derived nothing certain can be said at the present state of our knowledge. The