Items found in NJ

[Cae2g]

Hello! 
 

We found these two items in Monmouth County, NJ over the weekend. They were in a stream. They may just be rocks, but they look different than anything else we found! If you have any idea if they are rock or something else, I would love to know. Pen included for size. Thank you! 

[debivort]

It could be an internal cast of a bivalve, a "steinkern"

 

edit: it might also just be a concretion that is mollusk shaped. I'm not certain.

Edited May 8, 2023 by debivort

[njcreekhunter]

These are concretions. 

[Cae2g]

Thank you!

 

[frankh8147]

Yeah these are concretions but keep looking, the Monmouth County streams are LOADED with fossils.