Smooth brown turban snail

Norrisia norrisii has a wide, solid, shell that ranges in size from a few mm in juveniles up to 59 mm in adults, as measured across the greatest shell dimension. The shell is smooth, save for light growth lines and ill-defined spiral lines. It is brown or reddish fawn-colored, black around the umbilicus and greenish inside. Similar to other trochid snails, such as the more commonly occurring Chlorostoma species (or Tegula), the dextrally coiled shell of Norrisia norrisii is also more globose and shows a depressed-turbinate shape. The spire is low-conoidal. The minute apex is subacute, and spirally striate ; when perfect, the apical whorls are variegated. The 6 whorls widen rapidly. They are nearly plane and sloping above. Their edges project outside. They are pa23ery and rolled up like a spiral cord. The body whorl is very large. The thin peristome is simple. The sutures are plain. Other distinctive features include a smooth, green columella, an open, black-ringed umbilicus. The columellar margin is thickened at the base of the shell, and has a very obtuse tubercle there. The rounded-quadrangular aperture is angular above and brilliantly nacreous inside. It is sealed with an operculum made of protein rather than calcium carbonate. The operculum is circular, multispiral, with a central nucleus. The fleshy foot of the snail is a bright reddish orange with black speckling lining the basal margin. Four elongate epipodial tentacles are spaced evenly along both sides of the muscular foot. Empty shells of Norrisia norrisii are often occupied by hermit crabs, using the hard shell to protect their poorly armored posterior.