The Collaborative International Dictionary of English v.0.48:

Pipa \Pi*pa\, n.; pl. Pipas. (Zool.)
   The Surinam toad (Pipa Americana), noted for its peculiar
   breeding habits.
   [1913 Webster]

   Note: The male places the eggs on the back of the female,
         where they soon become inclosed in capsules formed by
         the thickening of the skin. The incubation of the eggs
         takes place in the capsules, and the young, when
         hatched, come forth with well developed legs.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Pipa americana
    n 1: a South American toad; incubates its young in pits in the
         skin of its back [syn: Surinam toad, Pipa pipa, Pipa
         americana]