Sperosoma biseriatum Döderlein, 1901

Fig. 20 A–C.

Sperosoma biseriatum: Döderlein, 1906: 150 –153. Pl. XIX, Fig. I. Pl. XL, Fig. I; Mortensen, 1935: 191 –193. Pl. XI, Figs 1–2. Pl. LXXVI, Fig. 13; Clark & Courtman-Stock, 1976: 221; Schultz, 2011: 1102, Figs 1930–1931. Echinosoma petersii: H.L. Clark, 1923:375; 1924:5.

Material examined. None, entry based on the literature.

Identification. Preserved test fragile, with irregularly arranged tubercles, larger tubercles restricted to ambitus. Pore-pairs in oblique/horizontal arcs, forming three ventral series. Preserved specimen reddish-brown.

Global maximum size. Maximum test diameter 120 mm.

Global distribution. East Africa and Arabian Sea, East coast region of South Africa, at 800–1020 m depth (Clark & Courtman-Stock 1976).

Remarks. Mortensen (1935) reports on specimens from the “ South African Marine Survey ” but neglects to give locality data. Record of species in Natal is based on Mortensen (1935) suspecting Clark’s (1925) Echinosoma petersii entries to be S. biseriatum (Clark & Courtman-Stock, 1976) . Unfortunately, there is no specimen of this species in the Iziko Museum, thus we were unable to verify this record. Differs from Hygrosoma petersii in that the tubercles diminish in size towards mouth, rather than totally disappearing.