Stephanocyathus weberianus

Stephanocyathus (Odontocyathus) weberianus (Alcock, 1902), comb. nov

Stephanotrochus weberianus Alcock, 1902a:101–102; 1902c:25, pl. 3: figs. 22, 22a.

Stephanotrochus Sibogae Alcock, 1902a: 102–103; 1902c:25–26, pl. 3: figs. 23, 23a.

Stephanotrochus sp.—Alcock, 1902c:26.

Stephanocyathus (Odontocyathus) ixine Squires, 1958:54 [in part: pl. 8: figs. 3, 4]

Stephanocyathus nobilis.—Zou. 1988:74–75 [in part: pl. 1: figs. 1–3].

DESCRIPTION.—Corallum bowl-shaped, with a flat to slightly convex base up to 26–28 mm in diameter, beyond which the thecal walls are inflected upward at an angle of 75°-80° from the horizontal. At level of thecal inflexion there are often 12–18 costal tubercles, each up to 2 mm long, one corresponding to each C1–2 and those C3 in which that half-system possesses 4 C5. Usually, however, the entire base and several mm of the lower thecal edge are completely eroded, which causes the tubercles to appear quite worn or to be absent. Tubercles often best developed on small coralla, before basal erosion occurs. In some coralla, thecal region corresponding to costal tubercles appears ‘swollen’ into a thick rim encircling the corallum base. Largest specimen examined (Alb-4969) 41.8 mm in calicular diameter and 22.2 mm in height. Costae on thecal perimeter slightly convex and granular, the C1–2 being slightly wider than other costae and ridged near the calice. Corallum white.

Septa hexamerally arranged in 5 cycles, the last incomplete, according to the formula: S1–2S3S4>S5. Large specimens (e.g., GCD > 40 mm) have only 72 septa, whereas mid-sized coralla of GCD 25–37 mm have only 64–70, and smaller coralla 18–25 mm GCD have 50–68 septa. No specimens were found with only 48 septa. Half-systems within a single specimen quite variable in development, some having 0, 2, or 4 S5. S1–2 highly exsert (about 5 mm), each bearing a low, oblique to almost horizontally projecting paliform lobe that extends into the columellar region. S3 slightly less exsert (3.0–3.5 mm), each also bearing a small paliform lobe but positioned slightly higher in fossa and slightly farther from columella than P1–2. S4 smaller still (only about 2.7 mm exsert), each bearing a wide paliform lobe which contributes to a palar crown that is located higher and farther recessed from the columella than the P3 crown. Inner edges of P4 usually bend toward and are fused to P3 near columella. S5 rudimentary, extending as narrow lamellae only partially down inner theca. When S5 are absent from a half-system, the S3 bears a wide paliform lobe equal in size and position to that of a P4. All septa have very finely sinuous inner edges and virtually smooth septal faces. All paliform lobes separated from their respective septa by broad, shallow notches. Fossa moderately deep, containing a papillose columella.