Smithsonian National Museum of Natural History

Original Description
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"Aulocyathus recidivus (Dennant, 1906) n. comb.

Ceratotrochus recidivus Dennant, 1906, pp. 159, 160, pi. 6, figs. 2a-2c.—Squires, 1961, p. 18; 1969, p. 16.—Zibrowius, 1980, p. 107.

Ceratotrochsu (sic) (Conotrochus) typus; Wells, 1958, pp. 265, 266, pi. 1, figs. 14, 15.

? Paracyathus conceptus; Squires and Keyes, 1967, p. 23 (part: C-648, pi. 2, figs. 7, 8).

Description. The following description is based primarily on the largest specimen from NZOI station C-734. Corallum ceratoid, straight with round calice. Corallum 10.3 mm in CD and 17.8 mm tall. Most specimens originally attached to internal sur face of fragment of parent specimen, from which they probably asexually budded. Some specimens originating from calice of unbroken parent specimen. Theca glossy, granular, sometimes marked by shallow striae. Costal granulation often indistinct and irregular. Calice usually round but maybe elliptical. Septa hexamerally arranged in four cycles. S1 larger than S2, these only slightly larger than S3. S4 smallest septa and never present as full cycle. Hexameral symmetry of younger specimens often not present; seven, eight, or nine groups of 4 or 6 septa often found. Large specimen with 40 septa includes two complete systems and four systems missing one pair of S4 each. Septa not exsert with straight, vertical inner edges. Septal granules small and blunt, uniformly distributed. Fossa deep. Columella composed of 11 individual, irregularly shaped rods.

Remarks. It is uncertain whether the corallum splits before the bud forms or whether the growing bud causes the corallum to fracture. Dennant (1906) implies the latter, whereas Marenzeller (1904a) implies the former for a related species, A. juvenescens.

Discussion. There are three other nominal species of Aulocyathus. A. recidivus differs from the two species known from off Japan, A. mactricidum (Kent, 1871) and A. conotrochoides (Yabe and Eguchi, 1932), by having a large, distinct columella. It differs from A. juvenescens Marenzeller, 1904 (off East Africa", 400-463), in being less slender and having fewer septa at a corresponding calicular diameter. Wells's (1958) specimen measures 11.6 mm in CD, is 25.6 mm tall, and has 60 septa. Squires's (1969) reference to A. recidivus from the Macquarie Ridge was undoubtedly from NZOI station C-734.

Material. NZOI sta. C-734 (9), USNM 47524. Golden Hind sta. 35 (1), MCZ. Specimen of Wells (1958) identified as C. (C.) typus from Discovery sta. 115, South Australian Museum H 51.

Types. The 'numerous' syntypes of C. recidivus are not at the Australian Museum (Zibrowius, 1980) and have not been traced further.

Distribution. Off southeastern Australia; off Tasmania; Macquarie Ridge (Map 5.) Depth range: 128-732 m." Cairns 1982, Plate 7, figs. 7-9; Plate 8, fig. 1