Source : Webster's Revised Unabridged Dictionary (1913)

Pika \Pi"ka\, n. (Zo["o]l.)
   Any one of several species of rodents of the genus {Lagomys},
   resembling small tailless rabbits. They inhabit the high
   mountains of Asia and America. Called also {calling hare},
   and {crying hare}. See {Chief hare}.

Chief hare \Chief" hare`\ (Zo["o]l.)
   A small rodent ({Lagamys princeps}) inhabiting the summits of
   the Rocky Mountains; -- also called {crying hare}, {calling
   hare}, {cony}, {American pika}, and {little chief hare}.

   Note: It is not a true hare or rabbit, but belongs to the
         curious family {Lagomyid[ae]}.