Rattus(redirected from Rattus norwegicus)
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The rats, a genus of rodents, family Muridae. Rattus rattus, the black r., is the species most commonly responsible for transmitting plague to humans by means of the flea, Xenopsylla cheopis; it is smaller and darker than the Norwegian, sewer, or brown rat (Rattus norvegicus) and has longer ears and tail. See: rat.