Part of a gooseneck barnacle? how big are they? the protuberance seems to be too large to be able to fit inside the case so maybe not a mollusc. Would like to see another pic, perhaps with something to judge the size

Look like a type of razor clams

I think seawillies is perfect!

Where I grew up (northeast coast) we called those long neck clams and YES, they are edible and delicious! Recipe:

1. Wash clams to remove any dirt or sand.
   2, In a large pot, heat oil over medium heat. Add garlic; saute for 1 minute, or until tender. Pour in the white wine. ...
2. Add clams, cover, and steam till clams start to open. Add butter, cover, and cook till most or all of the clams open. Discard any that do not open.

[allrecipes.com]