  The concept of a normal surface in a triangulated, compact 3-manifold was
generalised by Thurston to a spun-normal surface in a non-compact 3-manifold
with ideal triangulation. This paper defines a boundary curve map which takes a
spun-normal surface to an element of the direct sum of the first homology
groups of the vertex linking surfaces. The boundary curve map is used to study
the topology of a spun-normal surface as well as to determine the dimension of
the projective solution space of the algebraic equations arising from the
quadrilateral coordinates of spun-normal surfaces.
