Tectarius pagodus is a species of sea snail, a marine gastropod mollusk in the family Littorinidae. That family is commonly known as the winkles or periwinkles.
Description This species is the largest member of the genus Tectarius, and (like the rest of the family Littorinidae) is an herbivor.Harasewych, M.G. and Moretzsohn, Fabio. The Book of Shells: A Life-Size Guide to Identifying and Classifying Six Hundred Seashells, p. 827 (University of Chicago Press, 2014).
Distribution This species is endemic to the Indo-Pacific.Vermeij, G.J. "Molluscan marginalia: Serration at the lip edge in gastropods", Journal of Molluscan Studies (2014). It can be found in the upper part of the intertidal zone along rocky shores, and therefore does not often get submerged.
References
Further reading Reid, D. G. 1989. The Comparative Morphology, Phylogeny and Evolution of the Gastropod Family, Littorinidae. Philosophical Transactions of the Royal Society B, 324: 1–110.