What is a small European rodent of the genus Myoxus, of several species. They live in trees and feed on nuts, acorns, etc.; -- so called because they are usually torpid in winter called?

dormouse — A small European rodent of the genus Myoxus, of several species. They live in trees and feed on nuts, acorns, etc.; -- so called because they are usually torpid in winter. (Webster's 1913.)