Range: Hawaii and Polynesia to Natal.
Regional locality data: NORTHERN MOZAMBIQUE: Conducia Bay (NM H230, H5639: K. Grosch). SOUTHERN MOZAMBIQUE: 5 mi. N.W. of Bazaruto Is., 9 fath., on coral (NM G6033, J5796: Mrs E. Roscoe). NATAL: off Durban Bluff, 20-22 m, sand (NM B5460: R. K., R. Fregona); Scottburgh, beach-drift (NM 3287: C. W. Alexander, recorded Tomlin 1923); Shelley Beach, near Port Shepstone, beach-drift (NM 5964: R. K.).
Notes: M. atramentosa has recently been figured and described by Cernohorsky (1978) and Kay (1979). Its systematic position in the Turridae was confirmed by Orr (1959).
Protoconch orthoconic, of 2,5 smooth, gently convex whorls, its apex acute; rather vitreous, apex tinted with dark brown, end of last whorl with two faint brown spiral bands; breadth 0,45 mm, height 0,43 mm (b/h 1,05).