I found this on an Oregon beach. I thought for sure it was a tooth, but can't find any matches. Does anyone recognize it as a shell or a tooth? Here are photos (two are a little blurry, but you can see the shape) Also, it is about 1 inch wide, and is a little more textured than the photos appear (like a human tooth with small ridges)

http://www.badongo.com/pic/2492190

http://www.badongo.com/pic/2492194

http://www.badongo.com/pic/2492195

Thanks,
Chrissy

I took some better pictures. These look pretty true to what it is. Thanks for your help.

http://www.badongo.com/pic/2492267

http://www.badongo.com/pic/2492270

http://www.badongo.com/pic/2492272

http://www.badongo.com/pic/2492274

Looks like the eighth plate from a chiton.

Yes, this is the 8th plate or tail plate from Amicula stelleri, formerly called Cryptochiton stelleri, the Giant Pacific Chiton. Unlike most chiton species, the 8 shell plates of this species are completely internal, therefore not visible in the living animal.

Thank you so much for your knowledgeable response! This is a great resource.

Here's a view of all 8 plates:

http://members.cox.net/mollusca/stelleri.jpg

Also, I notice that in American Seashells, Abbott states the opposite of what I said above. According to Abbott, the current name (when the book was published over 30 years ago) was "Cryptochiton stelleri, formerly known as Amicula stelleri".