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figs. 2, 3.—Kikuchi, 1968:8—Fadlallah, 1983a: 135.—Cairns, 1989a:56-
57, pi. 29: figs, g-i [not Alb-5083] [synonymy].
Not Flabellum japonicum.—Marenzeller. 1888a:45-46 [= F. deludens].
DESCRIPTION.—Corallum campanulate, but laterally compressed,
with gently rounded, slightly convex thecal faces and
a sharp, crested thecal edge. Angle of thecal edges, 90°-108°;
inclination of lateral faces, 65°-88°. GCD:LCD = 1.3-1.4.
Largest specimen known (YO69-37-39) 57.6 x 39.5 mm in
calicular diameter and 37.0 mm in height. Thecal edge crests up
to 2.0 mm in height, but rarely extend to the calice of a
medium- to large-sized specimen. Pedicel size constant
throughout ontogeny, 2.5 x 2.0 mm in diameter and 2.0 mm in
height The 10 C,_2 occurring on thecal faces slightly raised as
rounded ridges. Fine chevron-shaped thecal growth lines occur
between all costae but C5; theca otherwise smooth, not
granular. In well-preserved specimens, calicular edge regularly
serrate, with an equilaterally triangular apex up to 3.5 mm in
height corresponding to each S1-2, a smaller apex of about 1.3
mm in height corresponding to each S3, and a very small apex
about 0.5 mm in height corresponding to each S4. Theca and
septa thin and fragile, theca of lower half of corallum often
discolored. Upper, fresh theca white or reddish brown, with
more intense pigmentation occuring in stripes overlaying the
C1-2 and upper, inner (thecal) edges of S^.
Septa hexamerally arranged in 5 cycles according to the
formula: S1_2>S3>S4»S5. S1-2 have vertical, highly sinuous
inner edges that define a deep, elongate fossa. S3 about
three-quarters width of an S1 and also have sinuous inner
edges. S4 half to three-quarters width of an S3 and have sinuous
inner edges that often loosely join to their adjacent S3 low in
fossa. S5 rudimentary, extending only partially down inner
theca. Lower, inner edges of S.|_2 form a rudimentary
columella; inner edges of S3 barely attain columella.
DISCUSSION.—Large, well-preserved specimens of F.
japonicum are easily distinguished from F. deludens by having
less serrate calicular margins (i.e., equilateral calicular apices
vs rectangular). If the calicular edges are broken, which is
common, F. japonicum can be distinguished by having less
prominent edge crests near the calice; a less open corallum (a
smaller edge angle); the presence of S5 adjacent to S,^; and
smooth, nongranular theca. Small specimens (GCD < 20 mm)
are virtually indistinguishable. Comparisons to the closley
related F. apertum borealis are made in the account of that
species.
MATERIAL EXAMINED.—New Records: YO69-3, 3,
USNM 92828; YO69-37-39, 3, USNM 92829, 2, ORI.
Previous Records: One syntype of F. japonicum; specimens
from off Japan and the Philippines reported by Cairns (1989a).
TYPES.—Eight syntypes of F. japonicum are deposited at the
BM (uncataloged). Type Locality: Challenger-232: 35° 1IX
139°28'E(Sagami Bay), 631 m.
DISTRIBUTION.—Japan: Off southeastern Honshu from Sagami
Bay to off Owase; Kii Strait, Shikoku; off Amakusa
Islands, Kyushu; 119-631 m. Elsewhere: Philippines, Indonesia;
128-1141 m.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
Flabellum (U.) apertum borealis, subsp. nov.
PLATE 32/,/-/
Not Flabellum cf. apertum.—Yabe and Eguchi, 1942a:89, pi. 5: fig. 12a-c;
1942b: 136. pi. 12: fig. 3a-c [= IF. deludens].
Flabellum apertum.—Cheng, 1977:135-137,6 figs.
Flabellum japonicum.—Cairns, 1989a:57 [in part: Alb-5083].
DESCRIPTION.—Corallum campanulate and laterally compressed,
the thecal edges forming a sharp angle but not crested.
Angle of thecal edges, 90°-112°; inclination of lateral faces,
54°-75°. GCD:LCD = 1.17-1.32. Largest specimen examined
(Alb-5086) 35.3 x 30.4 mm in calicular diameter and 31.6 mm
in height. The 4 lateral C, are invariably ridged for a short
distance about 9-14 mm above pedicel; C2 not expressed. In
well-preserved specimens, calicular edge is serrate, having a
tall, isosceles triangular apex up to 4 mm in height corresponding
to every S1-2 anc * a smaller apex corresponding to each S3.
Pedicel invariably eroded, the lower half to three-quarters of
theca often discolored. Theca porcellaneous, without granulation;
coralla often white or reddish brown with darker pigment
overlaying the C1-2.
Septa hexamerally arranged in 5 cycles according to the
formula: S1_2>S3>S4»S5, small specimens (GCD < 24 mm)
have only 48 septa, but larger specimens (GCD > 30 mm) have
a full fifth cycle. Su2 have vertical, sinuous inner edges that
define a very narrow, elongate fossa. S3 two-thirds to
three-quarters width of S^ and also have sinuous inner edges
but do not fuse with the columella. S4 about half width of an S3
and do not fuse to adjacent S3. S5 rudimentary. Lower, inner
edges of S^_2 form the rudimentary columella.
DISCUSSION.—This subspecies is similar to F. apertum in
that both taxa have campanulate coralla and 6 ridged (but not
crested) Cv The Japanese subspecies differs in its tendency to
have an additional cycle of septa (S5) and thus more closely
spaced septa. Flabellum apertum borealis also has a lesser
upward inflection of its thecal faces above the ridged C^ F.
apertum apertum having a fuller, more campanulate corallum.
Given the similarity of this form to typical F. apertum, but the
disjunct distribution of the two forms (F. apertum is known
only from the Subantarctic), this taxon is described as a
subspecies of Flabellum apertum.
Flabellum apertum borealis could easily be confused with F.
japonicum, but differs by (1) having protuberant (ridged) Cv
(2) lacking edge crests, (3) having S3 that do not extend to the
columella, (4) having a sharper calicular serration (isosceles
apices vs equilateral apices), and 5) living at a greater depth.
ETYMOLOGY.—The subspecies name borealis (Latin borealis,
meaning "boreal" or "northern"), refers to the disjunct
northern distribution of this subspecies.
MATERIAL EXAMINED AND TYPES.—Holotype: Alb-5086,1,
USNM 40710 (Plate 32/,/,/). Paratypes: Alb-4960, 1, USNM
40703; Alb-4969, 1, CAS 74943; Alb-4973, 2, USNM 40705;
Alb-5083, 1, USNM 40709, (Plate 32;,*;; off Jogashima,
Sagami Bay, depth unknown, 1, USNM 92841, 1, ORI; TM
(KT9202, ATI), 1, USNM 92842; TM (KT9202, YT5), 6,