The Collaborative International Dictionary of English v.0.48:

Tanka \Tan"ka\, n. (Naut.)
   A kind of boat used in Canton. It is about 25 feet long and
   is often rowed by women. Called also tankia. --S. W.
   Williams.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tankia \Tan"ki*a\, n. (Naut.)
   See Tanka.
   [1913 Webster]