North Cascades Mollusk ID

[PaleoRyder]

I recently found clam fossils in a river bed in the North Cascades (NW side of Kittitas County) that I'd love to identify. See attached image. Each fossil is approximately 3.5" long and 3" wide. 

[ClearLake]

While the shape is suggestive of a clam, I'm afraid those are stream eroded rocks.  The one on the far right may even be igneous, while the one on the left looks like shale/slate.  

[PaleoRyder]

Interesting. Thanks for the insight! How can you tell the difference? 

[PaleoRyder]

Also this one, which is much larger (see attached image).  

[ClearLake]

4 minutes ago, PaleoRyder said:

How can you tell the difference?

if you mean from a fossil clam, it is because I don't see any shell material, no ornamentation and no teeth that are found along the hinge of a clam.

 

If you mean the rock type, the one on the right looks like it has a fine crystalline texture while the one on the left shows distinctly layering,

[ClearLake]

No, sorry, looks like another rock.  A shell should have some very distinctive symmetry as well as exhibit either ornamentation (even though it can often be very subtle) or if it is from the inside, show some features such as muscle scars, teeth, ridges or indentations.  Check out some of the fossil shells in the images on the Forum here for some fine examples.

[I_gotta_rock]

10 hours ago, ClearLake said:

No, sorry, looks like another rock.  A shell should have some very distinctive symmetry as well as exhibit either ornamentation (even though it can often be very subtle) or if it is from the inside, show some features such as muscle scars, teeth, ridges or indentations.  Check out some of the fossil shells in the images on the Forum here for some fine examples.

While I agree that at least two of these are abiotic stone, an internal mold does not necessarily show any details. Some just pop out smooth and round. I've popped them out myself from cretaceous mollusks.  They could also be worn from the creek. Either way, they should show more than a smooth point at the beak.

 

The one on the left could, possibly, be a broken piece of a cast. It's not a permineralized shell or there would be layering visible on the broken side. The what would be the beak looks suspicious. The picture is pretty good, but I'd need to see it from all angles to really tell anything.

 

Do you know if there have been other fossils found in this creek?

[daves64]

Hiya neighbor (literally)! I currently exist in the same spot on the map.