Yes, those are sections of rudist shells, but unfortunately I cannot identify them further.

thank you dear sear

Axial sections in Rudists reef but it is hard to give a details

.

thank yous sear for your anser

cordially

As previously stated by Stevens and El Hassi, they are rudists. With those sections is not easy to precise genus or species, but in the first picture at the right side, one of the specimens shows a typical reticulate structure of the wall that copuld be usefulo to identify them.