Gyrineum hirasei is a highly distinctive, elongate species, resembling G. bituberculare in its tall spire and its very long anterior canal, but differing from G. bituberculare in its much smaller maximum size (although a single South African specimen I have examined is as large as an average-sized G. bituberculare), its straight spire outlines, its still taller spire, its very consistent fine, cancellate sculpture, and its completely consistent, distinctive, pale, pinkish orange to bright yellow-orange colour with vaguely defined white subsutural and basal bands. Specimens dredged alive have a thick, slightly felled to densely bristled, pale brown periostracum covering the entire teleoconch. The protoconch has 2.2 whorls. Although G. hirasei was described as a species of Biplex, it lacks the widely extended varices of Biplex and appears to be most similar to Gyrineum bituberculare.

Specimens of G. hirasei are known from a depth range of 80-390 m, from Japan (as far north as Okino-Yama Bank, off Boso Peninsula, Honshu; TSUCHIDA & KUROZUMl, 19%). the Philippine Islands, eastern Indonesia, New Caledonia and South Africa. In South Africa, it has been collected from west of the Mtamvuna River (to about 30° 18' E) eastwards at least to Sodwana Bay, near the Mozambique border (implying that it occurs further north in the western Indian Ocean). These records indicate a range encompassing the Indian Ocean and the western Pacific archipelagoes.
This species has been recorded previously only from Japan ("uncommon at about 100 m depth from Enshu Nada, Honshu to Tosa Bay. Shikoku"; HABI . 1964; 71) but I have seen a few specimens from the Philippine Islands (most specimens so identified from the Philippine Islands have proved, however, to be G. longicaudatum). In view of this recorded distribution, it was of some surprise to receive nine lots from South Africa on loan from the Natal Museum, and to realise that G. hirasei is the most common species of Gyrineum in dredgings off South Africa. Four lots are also present in MNHN collections from off the Tanimbar and Kai Islands in eastern Indonesia, and two juvenile specimens are present in collections from the Loyalty Ridge. New Caledonia, so this species probably occurs widely in the Indo-West Pacific in about 100-400 m of water. Protoconchs of South China Sea and South African specimens have 2.2 whorls whereas a Loyalty Ridge specimen has 1.9 whorls.