This specimen was found in the Pittsburg Bluff formation (Oligocene) in loosely consolidate sandstone. Due to the large opening and smooth shell I believe it to be a Neverita. Although the location is near the town of Pittsberg Oregon, I can't recommend it for the faint of heart (you are about 4' from the traffic which is mostly log trucks going > 55 MPH). However that being said the talus at the bottom of this formation is a marine invertebrate hunters gold mine. There was one piece of the sandstone that was fairly large (over a meter long) and it and every stone beneath had fossils. Most of the rocks in talus were covered with mud and water. This was only 2 days ago, so I have barely start to ID stuff. Here is my first find, just like this laying in talus covered with mud and water. Specimen is 5mm wide by 10mm long.
Quite happy with location and the condition of the fossils.