Aulocyathus matricidus (Saville Kent 1871)

Aulocyathus matricidus (Kent, 1871)

Flabellum matricidum Kent, 1871:276. pl. 23: fig. 2a–c.

Fragilocyathus conotrochoides Yabe and Eguchi. 1932a:388, 389, fig. 1; 1941b: 101: 1942b:ll6, 145, pl. 9: fig. 15.—Eguchi, 1965:288, 4 figs—Eguchi and Miyawaki, 1975:57.—Zibrowius. 1980:105. 107.

Aulocyathus cf. matricidum.—Yabe and Eguchi, 1941b: 101.

Aulocyathus cf. matricidus.—Yabe and Eguchi. 1942b: 112, 116.

DESCRIPTION.—Corallum elongate-conical, up to 31.0 mm in length but with a maximum calicular diameter of 8.5 mm (Yabe and Eguchi, 1942b). Illustrated specimen (TM (KT7802, Z4)) only 16.4 mm in length and 6.2 mm in diameter, tapering gradually to a broad pedicel 2.1 mm in diameter. Coralla appear to reproduce predominantly by budding from corallum fragments following the longitudinal fission of a parent corallum. Theca rough and striate, possessing twice the number of longitudinal ridges as septa. The true costae, those ridges corresponding in position to the septa, are 0.18–0.20 mm wide; whereas, between each costa occurs another narrower ridge 0.10–0.11 mm in width. Both ridges bear hollow, conical, apically inclined granules, many of which are abraded apically revealing a hollow interior. Corallum light brown.

Septa hexamerally arranged in 4 cycles, the fourth cycle rarely complete. Each system of a typical corallum contains 1 S2, 2 S3, and only 2 S4, resulting in a corallum total of 36 septa. As the corallum increases in size, additional pairs of S4 are added, completing various systems. Yabe and Eguchi (1942b) reported specimens of GCD = 6–8.5 mm to have 36–49 septa; the holotype of F. conotrochoides (GCD = 6.6 mm) has 44 septa; specimens reported herein (GCD = 5.2–7.5 mm) range from 38–40 septa; and a syntype of F matricidum (GCD = 7.4 mm) has 40 septa. S1 only very slightly exsert (0.5 mm) and have vertical, straight to slightly sinuous inner edges, which become quite thick (up to 0.7 mm) and coarsely granular to tuberculate at their lower edges. S2 about three-quarters width of an S1 and also have thickened, tuberculate inner edges, sometimes bearing a narrow paliform lobe or columellar process that extends upward into the fossa. S3 that are flanked by a pair of S4 are about three-quarters width of an S2 and have thick inner edges; S3 that stand alone are only half width of an S2 and have coarsely dentate, narrow inner edges. S4 similar in shape to those S3 unflanked by S4. Upper outer edges of septa not notched near thecal edge. Fossa deep. Columella rudimentary, composed of the tuberculate, widened lower inner edges of the S1–2 and often a single rudimentary tubercle.

azooxanthellate

84-207 m