Cyathotrochus pileus (Alcock 1902)

Tropidocyathus pileus (Alcock, 1902)

Trochocyathus pileus Alcock, 1902a:96–97; 1902c:15–16, pl. 2: figs. 11, 11a.—Yabe and Eguchi, 1942b: 123, pl. 10: figs. 19, 20.—Eguchi, 1965:286, 2 figs.

Trochocyathus (Tropidocyathus) intermedius Yabe and Eguchi, 1932b:443 [nomen nudum].

Tropidocyathus pileus.—Cairns, 1989a:34–35, pl. 17: figs, a–h [synonymy].

DESCRIPTION.—Looking at a lateral face, the corallum is trapezoidal, the lower lateral edges being either rounded or slightly protuberent, but never cannate (crested). Largest Japanese specimen examined (TM (KT9015, BS2)) 18.7 × 11.0 mm in calicular diameter and 19.5 mm in height. Costae continuous from calice to base, where many are continuous with their counterparts from the opposite face. Edge protuberances, if present, vertically costate and not granular. Costae rounded and equal in width, each bearing an outer unilinear row of coarse teeth, as well as smaller granules on their lateral faces. Intercostal furrows deep. Corallum white.

Septa hexamerally arranged in 4 cycles, larger specimens having pairs of S5 in their end half-systems, e.g., the illustrated specimen has 6 pairs of S5 for a total of 60 septa. S1 about 2 mm exsert and have slightly sinuous inner edges, each S1 bordered by a small (about 0.8 mm wide), highly granular palus that is positioned directly adjacent to the columella. S2 only slightly less exsert and about 80% width of an S1, each S2 also bearing a palus of equal width and position to that of the P, but rising higher in the fossa. S3 least exsert septa (only about 1 mm) and about two-thirds width of an S2, each having a broad (about 1.5 mm wide) palus slightly recessed from the columella and rising higher in the fossa than the P2. Each pair of P3 within a system slant toward their flanked P2, the inner edges of these triads (1 P2 and 2 P3) sometimes loosely fused into a chevron arrangement. S4 slightly more exsert and wider than S3, their outer edges fused to adjacent S1–2 at calicular edge producing calicular projections that result in a serrate calicular margin. P4 present only if pairs of S5 present in a half-system. Fossa of moderate depth. Columella linear-papillose, the elements strongly fused together into a solid lamella.

Tropidocyathus pileus (Alcock, 1902)

?Tropidocyathus bougainvillei Milne Edwards and Haime, 1857:57.

Trochocyathus (Trochocyathus) pileus Alcock, 1902a:15–16, pl. 2: figs. 11, 11a.—Faustino, 1927:81, pl. 7: figs. 7, 8.—Yabe and Eguchi, 1942b:123, pl. 10: figs. 19, 20.

?Cyathotrochus herdmani Bourne, 1905:193, pl. 1: figs. 2, 2a.

Trochocyathus (Tropidocyathus) intermedius Yabe and Eguchi, 1932b:443 [nomen nudum].

Not Trochocyathus pileus.—Gardiner and Waugh, 1938:187 [= Premocyathus sp.].

?Tropidocyathus nascornatus Gardiner and Waugh, 1938:193–194, pl. 5: fig. 10.

Trochocyathus pileus.—Eguchi, 1965:286, 2 figs.

DESCRIPTION.—Corallum variable in shape, ranging from trapezoidal (Plate 17d), to campanulate (Plate 17a), to triangular, the first two shapes having rounded bases, the latter having a slender, slightly curved base. Largest specimen examined (ALB-5506) 25.7×17.3 mm in calicular diameter and 18.8 mm tall. Calice elliptical, almost obscured by highly exsert septa; GCD:LCD = 1.5–1.65. No edge crests; however, in some trapezoidal and campanulate specimens the principal C1 and two adjacent C4 (or C5) are quite prominent near the base (Plate 17f,h). Except for these costae, all others extend to the base of the corallum where they join their counterparts from the opposite face. Costae of equal width (0.36–0.39 mm), separated by deep intercostal furrows 0.18–0.25 mm wide. In larger coralla the intercostal space is much broader, up to 0.5 mm, and as much as 1 mm deep. This occurs because, as the corallum grows larger, its calicular circumference increases but the number of costae (48–56) and their width remain the same. Each costa bears a uniserial row of large, closely adjacent, blunt teeth, each about 0.22 mm in basal width, their appearance described as “milled” or serrate by Alcock (1902a). The lateral edges of each costa also bear smaller pointed granules up to 0.2 mm tall; the intercostal theca smooth. Corallum white.

Septa hexamerally arranged in four cycles, larger specimens having one or two pairs of S5 in four half-systems adjacent to principal septa, for a total of 56–64 septa. S1 highly exsert (up to 5 mm), with straight, vertical inner edges and a small, independent lamellar P1 on its inner edge. In only one specimen, Alcock's (1902a) figured syntype, are the inner edges of the S1–2 grooved in the manner of T. lessoni. S2 only slightly less exsert, also having a straight, vertical inner edge and a similar sized P2, but one that extends slightly higher in the fossa. S3 least exsert of all septa (about 1 mm), each bordered by a broad palus about twice as broad as the P1–2. P3 slightly recessed from columella and rise higher in fossa than other pali. As in T. lessoni, each pair of P3 fuses with the enclosed P2 in its septal system to form a V-shaped structure. S4 moderately exsert (up to 3 mm), the theca between the S4 and adjacent S1 or S2 raised about 2 mm, forming 12 rectangular projections around the circumference of the calice. S4 extend slightly farther toward columella than S3, their inner edges slightly overlapping and loosely fusing to the P3. If pairs of S5 are present, small P4 are also present, each about the same size as a P1 and recessed from the columella even more than the P3. Septal and palar granules about 0.15 mm tall but quite scarce, resulting in relatively smooth septal faces. Septal granules vertically aligned short carinae in syntypes.

Fossa relatively shallow, filled with three cycles of pali and the columella. Columella variable in shape, ranging from a thin lamella to several basally fused, crispate papillae, to a spongy mass.

azooxanthellate

123-522 m