the echinoid fauna from japan and adjacent regions part i

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Test small to very large in size, usually hemispherical, but it may be either
more flattened or higher, almost egg·shaped. Ambulacra with compound, trigeminate,
of generally diadematoid structure, or polyporous plates, rarely with simple plates
adapically; a diplopodous arrangement may occur adapically or throughout the am·
bulacra. Primary tubercles imperforate, non·crenulate. Apical system usually small,
dicyclic, or monocyclic, rarely slightly extending into the posterior interambulacrum
(5), or oculars becoming insert in the sequence I, V, IV. Peristome generally rather
large; gill·slits may be rather large and deep. Pedicellariae, in the Recent form, of
the ophicephalous, tridentate, triphyllous and globiferous types. Sphaeridia placed
along the tube· feet, not in pits (from MORTENSEN, 1935).
From the Lias (Domerian) to Recent.
The relations of Stomechinus and allied forms have been the object of puzzling
among authors on the Echinoids, until MORTENSEN (1935, pp. 496, 504) clearly showed
their relationship to the living Stomopneustes founded on their typically stirodont teeth
and on the character of the test. Accordingly, it now becomes clear that the affinity
of Stomechinus and allied genera in with the Phymosomatids, and with Stomo pneu·
stes among the Recent sea·urchins, the latter genus being the only living representa·
tive of the once flourished group (with about fifteen genera) during the Jurassic
and Cretaceous Periods. Just like Glyptocidlaris (ioc. cit.) is, the only Recent repre·
sentative of that group of fossil Echinoids, the Phymosomatids (with nearly twenty
genera and subgenera). A direct comparison between Stomechinus (St. bigranlllaris
(LAMARCK, 1816) is in IGPS colI. cat. no. 5202) and the living Stomopneustes shows
them to be so very alike in all the main characters that they should be classified
into one group.
By their imperforate, non·crenulated tubercles, together with the structure of
ambulacral plates ,particularly in the Stomopnellstes), and the complete reduction of
the cortex layer on the spines, the Stomechinids (Stomopneustids) are regarded as
the most specialized forms of all the Phymosomatoina.
There is only a fossil species of the genus Stomopnellstes in our collection, as
described herein.
Genus Stomopneustes AGASSIZ, 1841
Stomopneustes AGASSIZ, 1841, p. 7.-AGASSIZ, 184l-a, p. x.-A. AGASSIZ, 1872-74, pp. 161, 436.
-TE;\;ISON·WOODS, 1878, p. 150.-ZITTEL, 1879, p. 509.-STEWART, 1880, p. 91l.-BELL,
1881-a, p. 424.-POMEL, 1883, p. 79.-DuNCAN, 1889-a, p. 119.-MoRTENSEN, 1903-b, p.133.
-DELAGE and HEROUARD, 1903, p. 24l.-MEISSNER, 1904, p. 1362.-H. L. CLARK, 1912-b,
p. 229.-DJAKOP;OV, 1923, p. 222.-H. L. CLARK, 1925, p. 68.-TORTONESE, 1933, p. 1l0.­
MORTENSEN, 1935, p. 505.-H. L. CLARK, 1946, p. 305.
Orthotype.-Echinus variolaris LAMARCK, 1816, p. 47 (Les mers australes).-Stomopneustes
variolaris (LAMARCK) A. AGASSIZ, 1872-74, p. 437, pI. 4b, figs. 1-3 (Indian Ocean).-MoR.
TENSEN, 1935, p. 507, pI. 71, figs. 3-5, pI. 72, figs, 1-2, pI. 89, figs. 16-26, text·figs. 301-302
(Indo·West Pacific, littoral).
Heliocidaris AGASSIZ and DESOR, 1846, p. 371.-A. AGASSIZ, 1863, p. 22.-COTTEAU, 1861-67
(67), p. 819.
Logotype.-Echinus variolaris LAMARCK, 1816, p. 47. [Cotteau, 1861-67 (67), p. 819J. (Non
Heliocidaris AGASSIZ and DESOR: MORTENSE;\;, 1903-b, p. 116-nec H. L. CLARK, 1912-b,
p. 281).