Below are examples of snails you are likely to run across if you spend any time at all on Oregon’s exposed rocky shores. All photos are from northern Oregon unless otherwise noted in the caption. My organization follows Lamb an Hanby (2005). Common names are my choice. I refer toWoRMS for scientific names, and I learn a ton by browsing the natural history riches in Kozloff (1993). Biodiversity of the Central Coast’s molluscs page is full of great information about most of the species shown below, and they are covered in the books, field guides, and identification resources listed at the bottom of the page.
Tegula funebralis, black turban
Black turbans are conspicuous and abundant. The seem a bit more numerous on the central Oregon coast than on my home beaches in northern Oregon, but that could just be the places I frequent.
The top of the shell is almost always eroded 
A variety of small invertebrates hitch-hike on Tegula shells 
Not much black at all, here
Dave Cowles’ page on back turbans is full of additional information.
References
Gotshall, D. W. 2005. Guide to Marine Invertebrates, Alaska to Baja California 2nd Edition (Revised). Shoreline Press.
Harbo, R. M. 2011. Whelks to Whales: Coastal Marine Life of the Pacific Northwest. 2nd ed. Harbour Publishing Co.
Kozloff, E. N. 1993. Seashore Life of the Northern Pacific Coast. 3rd ed. University of Washington Press.
Lamb, A. and B. P. Hanby. 2005. Marine Life of the Pacific Northwest. Harbour Publishing.
Sept. J. D. 2009. The Beachcomber’s Guide to Seashore Life in the Pacific Northwest. Revised ed. Harbour Publishing.
