The Collaborative International Dictionary of English v.0.48:

Viscacha \Vis*ca"cha\, Viz-cacha \Viz-ca"cha\, n. [Sp.] (Zool.)
   A large burrowing South American rodent (Lagostomus
   trichodactylus) allied to the chinchillas, but much larger.
   Its fur is soft and rather long, mottled gray above, white or
   yellowish white beneath. There is a white band across the
   muzzle, and a dark band on each cheek. It inhabits grassy
   plains, and is noted for its extensive burrows and for
   heaping up miscellaneous articles at the mouth of its
   burrows. Called also biscacha, bizcacha, vischacha,
   vishatscha.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Vizcacha \Viz*ca"cha\, n. [Sp.] (Zool.)
   Same as Viscacha.
   [1913 Webster]