PLATE XXX 
Unio senectus White. Judith River beds of the Cretaceous series. 
Fic. 1. Right side view of a broken specimen. 
Unio gonionotus White. Laramie Group of the Cretaceous series. 
Fic. 2. Right side view of an adult specimen. 
Fic. 3. Left side view of a younger one. 
Unio proavitus White. Laramie Group of the Cretaceous series. 
Fic. 4. Left side view of an adult specimen. 
Fic. 5. Front view of another adult. 
Fic. 6. Right side view of another specimen. 
Fic. 7. Interior view of a left valve. 
