Is this a crab fossil?

[Byron3]

This was found in wyoming

[JamieLynn]

In the second picture is a nice little gastropod fossil - possibly a turritella. While the actual rock does look surprisingly crab shaped, I don't think there is anything indicating crab other than the outline. I will let the experts weigh in, but not seeing "crabbly" here. Just an oddly shaped limestone ...but with fossils in it! So....yay! 

[caldigger]

This maybe an internal cast of a bivalve, but hard to really tell from the provided photos. However, I concur. Not a crab.

[Haravex]

Its not a crab but the last picture is definitely a fossil now it's an invertebrate, which is not my area of expertise I would suggest something along the lines of crinoid stem or a gastropod of sorts.