Sentence:  Passing by Conical Rock, an isolated peak which forms a conspicuous landmark, the coast trends to the northward to Cape Dudley Digges and on to Cape Athol. Beyond Cape Athol lies Saunders Island, at the entrance to Wolstenholme Sound, which like most of these inlets, forms the <WSD>embouchure</WSD> of a glacier-river. 
Meaning of the word marked with <WSD> tags:  The mouth of a river or valley.