the echinoid fauna from japan and adjacent regions part i

.26 S. NISIYAMA
impractical since it necessitated separating only several genera that are very similar
and related. They held a view that the orderof the Clypeastroids, as understood by
MORTENSEN (1948-cl and DURHAM (1955), to be a homogenous group of Holectypoid
ancestry; and by the characters of the adapical termination of the interambulacra,
this is, the continuity or not of the interambulacra on the oral surface, and the
position of the auricles, they divided this order into four well marked suborders; as
did the senior (DURHAM, 1955) of the two authors. 6. DURHAM and MELVILLE (1957,
pp. 259, 260, 266) proposed the new order Holasteroida to embrace two suborders
Protosternata and Meridosternata of MORTENSEN'S usage on the reason that the char­
·acters of their apical system are of sufficient importance to unite them in an order
than to divide into two suborders.
This brief review should give an impression of how the systematic arrangement
and the classification of the Echinoidea differ in various authors, and how different
nomenclatures are devised for a group of different ranks. Among the classifications
-established hitherto, that of MORTENSEN with an emendation of DURHAM and MEL­
VILLE seems to be most reliable, although he stated in his great work (MORTENSEN,
1951, p. 573) that-" It was only clear to me that I could not accept any of the clas­
:sification hitherto given in the literature, and my own classification was still in the
making". His material included the whole of Recent and fossil genera and subgenera,
and his classification is not based on a few, simple characters, but on nearly all the
·exceedingly numerous, diversified and complex skeletal structures, as well as the
larvae and the internal spicules. But the fact that so a large number of the genera
and subgenera are fossil (in which the paleontologist has disadvantage of the neontologist
in that pedicellariae, internal spicules, well preserved microstructure of spines,
·as well as the fact that the occurrence of such structures in place on the test in
fossil is uncommon), and thus only incompletely known, and there are so many gaps,
.beside lack of materials, naturally causes some uncertainties here and there. Future
fortunate finds of necessary fossils, which clear up the uncertainties, and future
embryological researches, which may prove the true genetic relations, may be expected
to consolidate the classification and the systematic arrangement of the great class of
the Echinoidea.
A NOTE ON TAXA OF THE ORDER-GROUP AND THEIR NAMES
As listed above, so many different nomenclatures have been tried for a rank
(group), particularly to a ordinal rank, of the Echinoidea by various authors, e. g.,
LAMBERT'S Pileatoida LAMBERT (suborder) corresponds to MORTENSEN'S Holectypina
GREGORY, and LAMBERT'S both of Brachygnatha (order) and Globatoroida approximately
correspond to MORTENSEN'S Echinoneina HAWKINS (suborder), that for the
use of these nomenclatures must be paid much caution. The International Code of
.Zoological Nomenclature have no codification on the nomenclature of ranks higher
than the ordinal group. In considering the name to be used for order-group DURHAM
and MELVILLE (1957, pp. 262-270), bearing in mind the recommondations published in
"Copenhagen Decision on Zoological Nomenclature", have approved to use uniform
·terminations for ordinal and subordinal names. They have used" -oida". by addition