Primnoella biserialis Wright & Studer 1889

Primnoella biserialis Wright & Studer, 1889

(Fig. 3 B)

Primnoella biserialis Wright & Studer, 1889: 87; May 1899: 16; Versluys 1906: 55; Kükenthal 1919: 399; 1924: 285.

Diagnosis. See Wright and Studer 1889: 87–88, pl. XVII, fig. 3, pl. XXI, fig. 14. Material examined. ARGENTINA, Chubut, San Matías Gulf, 41º13’S, 65º59’W, 30 April 1971, st. 110, 90 m, “Survey S.A. O. II”, (MLP s/n).

Description. Finely planar colony, branching dichotomously, 32 cm in height. Terminal branches whip­like. Polyps appear in whorls of 6–7 polyps, which are uniformly spaced along the stem. Polyps 1.2–1.5 mm in height. Polyp scales placed in two abaxial longitudinal rows with 13–15 scales. Scales with multituberculate warts. Opercular scales ovoid with concentric lines (0.087–0.10 mm wide and 0.15–0.21 mm long); triangulated marginal scales with a small terminal point (0.18 mm wide and 0.23 mm long); and basal and medial scales rounded, rectangular, polygonal (0.23 mm wide and 0.16 mm long). Coenenchymal scales rounded with few warts (0.06–0.1 mm wide and 0.098–0.15 mm long), small tuberculated rods (0.036 mm wide and 0.078 mm long) and a few tuberculate clubs (0.053 mm wide and 0.11 mm long).

Distribution (Fig. 1). Macaé (39 m) (Brazil), Montevideo (35º05’S, 52º33’W, 115 m) (Uruguay) (Tixier­Durivault 1969–70); Tom Bay (50º10’S, 74º42’W, 815 m) (Chile) (Wright & Studer 1889); Smyth Canal (15 m) (Chile) (May 1899); Burdwood Bank (54º 43' S, 60º 14' W, 202 m) (Broch 1965).

New record. San Matías Gulf, Chubut (Argentina).

Remarks. The present record is the first off the Argentinian continental slope.