Under-clays of the coal, [81].
Unio, [414].
United States, [256], [257], [364], [367], [399], [400].
Univalve mollusks, [378], [417].
Upper Silurian series, [33].
Upright trunks of sigillariæ, [125].
Ursus arctos, [811].
----- priscus, [812].
----- spelæus, [811].