One of the blocks of Salem limestone in the south steps of the church features a nautiloid (a cephalopod) almost two feet in length: 

 

Finally, in contrast to the Hoosier Paleozoic marine limestones visible from the outside, a much younger carbonate rock of non-marine origin and much more distant provenance is found in the floor of the foyer. It's a travertine, almost certainly of Quaternary age and probably quarried in Idaho or Italy.  

The change from ancent rugged Indiana limestones on the exterior to an exotic modern stone on the interior thus provides a symbolic architectural transition from the midwestern environment on the outside to something much younger and of non-Hoosier origin on the inside.