Helicosphaera pavimentum Okada & McIntyre, 1977
From Latin nudus = naked, referring to the absence of a blanket.
Coccolith has a helical flange and proximal plate without a blanket. The wall is confined to the central opening and does not impinge on the distal surface of the flange to become a blanket.
Okada, H. & McIntyre, A. 1977. Modern coccolithophores of the Pacific and North Atlantic Oceans. Micropaleontology 23(1): 1-55.