The Collaborative International Dictionary of English v.0.48:

Potto \Pot"to\, n. (Zool.)
      (a) A nocturnal mammal (Perodictius potto) of the Lemur
          family, found in West Africa. It has rudimentary
          forefingers. Called also aposoro, and bush dog.
      (b) The kinkajou.
          [1913 Webster]