Deltocyathus rotulus (Alcock 1898)

New Caldonia waters from 20°31’S to 23°54’S, 699-830 m (Kitahara & Cairns, 2009); Indian Ocean off Durban, off Mozambique, off Zanzibar (Cairns & Keller 1993), 510-1986 m, including Maldive islands (Alcock 1898; Gardiner & Waugh 1938), Gulf of Aden (Gardiner & Waugh 1938), off Sri Lanka (Van der Horst 1931), and off Tanzania (Gardiner & Waugh 1938); Pacifi c Ocean off southeastern Japan (Cairns 1994), 799-1187 m, off Philippines, Indonesia (Flores and Celebes Sea), Malaysia (Alcock 1902a, c; Cairns & Zibrowius 1997), 210-1719 m, Vanuatu and Wallis and Futuna region (Cairns 1999), 1050-1160 m, Australia region off Queensland (Cairns 2004), 143-1192 m.

Corallum circular to slightly elliptical with lancetted calicular margin. Each apex correspond to those C4 fl anked by C5. Base normally slightly conical and pointed in centre. Costae more prominent near calicular edge as low serrated ridges. C1-3 originates in centre of the base, C4 present only near calicular edge, and C5 slightly wider than C4. Corallum white to reddish-brown. Septa hexamerally arranged in 5 cycles (S1-2>S3> S4>S5). S1-2 do not fuse to any adjacent septa, each bearing a palus about 1-2.5 mm wide. S3 less exert with irregularly shaped paliform lobe, sometimes P3 wider than P1-2, but some specimens present P3 very small. Adjacent to the P3, near columella, sometimes 2 or 3 small paliform teeth are present. S4 less wide and exsert than S3 but bear a wide and tall palus, producing a prominent palar crown encircling columella. Each P4 fuses to the fl anked P3 near columella. S5 fuses to the axial edge of adjacent P4 close to basal theca through a long and porous lamella. Fossa extremely shallow containing a welldeveloped papillose columella composed of several interconnected rods.

Deltocyathus rotulus (Alcock, 1898)

Trochocyathus rotulus Alcock, 1898:16, pl. 2: figs. 1, 1a.

Deltocyathus fragilis Alcock, 1902a:99–100; 1902c:21, pl. 2: figs. 15, 15a.

Deltocyathus rotulus.—Cairns and Keller, 1993:245, fig. 51 [synonymy].

DESCRIPTION.—Corallum shaped like a shallow bowl, with a flat to gently rounded base and upturned edges. Largest Japanese specimen examined (Alb-5079) 31.1 mm in diameter and 7.3 mm in height; however, a specimen from the Celebes Sea (Alb-5582) is larger, measuring 36.4 mm in diameter. Circular region 7–12 mm in diameter at center of base of large coralla invariably worn and without costae. Otherwise, peripheral region of base crenulated, the theca associated with each C4 and flanking C5 forming slightly raised radial strips about 2 mm wide that project up to 1.5 mm beyond the calicular edge formed by the C1–3. C1–3 extremely narrow (about 0.2 mm), finely serrate ridges that are slightly recessed in valleys formed by ridged C4–5. Corallum white.

Septa hexamerally arranged in 5 cycles, the fifth cycle usually completed at a calicular diameter of 30–32 mm. Small coralla often lack all 4 S5 within one or more half-systems, a specimen 20–30 mm in diameter having anywhere from 72–92 septa. S1–2 moderately exsert (about 3 mm) and are independent septa, i.e., not fused to any adjacent septa. Each S1–2 usually bears a small palus (about 1 mm wide), which is separated from its septum by a relatively wide notch. S3 slightly less exsert and usually do not bear pali, but, if present, pali are irregular in occurrence and usually quite small. S4 equally exsert as S3, each bearing a very wide (up to 4 mm), tall palus, together producing a prominent and distinct palar crown of up to 24 lobes. In a half-system lacking all 4 S5, the S3 within that half-system resembles an S4 and has a correspondingly large palus. Inner edges of paired P4 merge with inner edges of adjacent S3 near columella. S5 rudimentary, each connected to its adjacent S4 through a porous lamella in the P4 region, but close to basal theca. Fossa shallow, containing a circular to elliptical columella in the form of an undercut, horizontal platform, through which irregularly shaped papillae penetrate.

azooxanthellate

210-1300 m