Devonian Catskill Fm unknown

[MeisTravis]

I was wondering if this is even a fossil or some kind of weird rock formation I found. It’s from NEPA in part of the catskill formation. Let me know what you guys think!! Basically all I’ve ever found there is trace fossils so I wasn’t sure if this is even anything. Thanks all!

[Fossildude19]

Looks like a nodule or concretion, to me.   

[Rockwood]

I've puzzled over similar shapes found at Limestone Hill, just north of Flagstaff Lake here in Maine. There seems to be a consistency in shape that suggests to me that they are a fossil. Beyond that the trail of evidence is faint to nonexistent though.  

[jdp]

Looks to me like a carbonate nodule. You get these in sediments with groundwater influence.

[fossilnut]

The shape resembles a internal cast of a bivalve Cucullea. I failed to check how far back they go. Not saying it is a fossil but has some resemblance. But some main distinguishing features are missing or eroded. These casts are commonly found as float in Myrtle Beach SC and from the Eocene in Maryland. They can be very large size. Some species are named giganor/giganta because of the size. But I have found some baby sized ones. The pictured one has some shell material remaining. The SC ones do not but are phosphate casts.

[Rockwood]

15 minutes ago, fossilnut said:

I failed to check how far back they go.

I suspect one would come up a bit short in that genus. But I'm being lazy about it too.