Webster’s Revised Unabridged Dictionary · 1913
Dyas
Dy′as, n. [L. dyas the number two.] (Geol.) A name applied in Germany to the Permian formation, there consisting of two principal groups.
Webster’s Revised Unabridged Dictionary · 1913
Dy′as, n. [L. dyas the number two.] (Geol.) A name applied in Germany to the Permian formation, there consisting of two principal groups.