A new name for Altivasum typicum Hedley, 1916 fide Dekkers and Maxwell, 2018 and the description of Altivasum clarksoni n. sp.

This paper addresses the taxonomy irregularity concerning Altivasum typicum Hedley, 1916 fide Dekkers and Maxwell, 2018 that has historically been synonymized under Altivasum flindersi Verco, 1914. We introduce the erection of Altivasum hedleyi n. sp. correcting this taxonomical conundrum that originated from the Hedley (1916) paper. Furthermore, this paper presents a new morph of Altivasum restricted to Esperance in Western Australia. Altivasum clarksoni n. sp. morphologically differs from Altivasum flindersi Verco, 1914 having solid pyramidal knobs on an acute shoulder and a form that is much more equi-biconic. Altivasum hedleyi nov. sp. is also sympatric in part with Altivasum clarksoni n. sp. but is much smaller and the early teleoconch differs in structural form. This paper brings the number of described Altivasum and their forms to four.