24 PLATE XI A. [Assembly 



Fossils of the limestone layers in the Marcellus shale. 



1. GoNiATiTES DiscoiDEUS, showing the septa. 



2. The same, showing the exterior form. 



3. GrONIATITES EXPANSUS. 



4. Same, back view ( p. 63). 



5. Nautilus ornatus. 



6. Same, hack view ( p. 64). 



