Nassarius arcularia, commonly known as the casket nassa or the little box dog whelk, is a species of sea snail in the Nassa mud snail or dog whelk family, Nassariidae. It is found in tropical and subtropical coastal waters across the world, inhabiting muddy areas close to the shoreline. The shell, which is very common, has a thickness of up to 3 centimetres (1.2 inches) and varies in form – for example, in the elongation of the whorls and the longitudinal folds – as well as in color, with some specimens entirely white while others have brown bands. The young of this species have folds and striae that are much more prominent. This composite photograph shows five different views of a N. arcularia shell, with a length of 2.2 centimetres (0.87 inches), that was collected in Madagascar.Photograph credit: H. Zell