We often get questions… “I found an egg case! But which species is it? It does look like anything in the ID guide!”
Our advice: soak it!
Look at the pictures below to see the difference between a dry egg case and an egg case that has been soaked for several hours.
Do not forget to register your find on eggcase.org (English) or eikapsel.org (Dutch). Both websites offer a free ID guide you can download and registration form. Through registration, you are citizen scientist, who works research that can help to determine breeding grounds and population size.

Dried out egg cases..

A soaked egg case is much larger! Left: Undulate ray, right: thornback ray

Could this be an undulate ray egg case???

It fits! It’s an undulate ray egg case!