PLATE XXXI 
Unio aldrichi White. Laramie Group of the Cretaceous series. 
Fic. 1. Left side view of a partially broken specimen. 
Fic. 2. Dorsal view of the same. 
Unio holmesianus White. Laramie Group of the Cretaceous series.. 
Fic. 3. Left side view of an adult specimen. 
Fic. 4.. Dorsal view of the same. 
Unio goniambonatus White. Laramie Group of the Cretaceous series. 
Fic. 5. Left side view; probably a male. 
Fic. 6. Dorsal view of the same. 
Unio stantoni new species. Laramie Group of the Cretaceous series. 
Fic. 7. Right side view. 
The specimen here figured under the name of U. stantoni, in honor of 
Dr. T. W. Stanton, was formerly referred to U. dane Meek and Hayden 
of the Judith River beds; but it proves to be different in specific features 
and to come from a much higher position in the Cretaceous series. 
