Newcomb's Littorine Snail

Geographical Range: Reported from Humboldt Bay, California to southern British Columbia

Depth Range: Very high intertidal

As with other members of family Littorinidae, the periostracum is present but not thick and hairy; There is no siphonal notch or canal. The shell height is greater than but not more than twice the diameter, with a clearly visible spire. The inside of the shell is not pearly. It does not have an open umbilicus. Littorina subrotundata has a shell that is higher than wide. The body whorl is fairly globose. The spire has about 4 whorls and tapers to an acute apex. The shell is thinner than that of most Littorina species and the whorls do not have spiral ridges. The aperture is about half the shell height and teardrop shaped. The margin of the columella curls and forms a narrow groove under it. The animal has a horny operculum. Brown with narrow whitish or light brown spiral bands. Maximum height 8 mm.

How to Distinguish from Similar Species: Few other littorinas live in the upper saltmarsh. An unnamed Littorina sp has evenly spaced dark brown and yellow bands and a bilaterally symmetrical aperture. It is found more commonly in Coos Bay, Oregon than in Washington waters. I have found Littorina sitkana in rather similar areas, but that species has spiral ridges on the shell.

Biology/Natural History: This snail has been a candidate for listing as an endangered species both by Washington State and by the U.S. Fish and Wildlife Service. I didn't find records of other people finding it in the Salish Sea.

In very high intertidal of salt marshes, on or near Salicornia.

Littorina subrotundata is a species of sea snail, a marine gastropod mollusk in the family Littorinidae, the winkles or periwinkles.