  We present an updated investigation of the relation between large scale disk
circular velocity, v_c, and bulge velocity dispersion, sigma_c. New bulge
velocity dispersions are measured for a sample of 11 low surface brightness
(LSB) and 7 high surface brightness (HSB) spiral galaxies for which v_c is
known from published optical or HI rotation curves. We find that, while LSB
galaxies appear to define the upper envelope of the region occupied by HSB
galaxies (having relatively larger v_c for any given sigma_c), the distinction
between LSB and HSB galaxies in the v_c-sigma_c plane becomes less pronounced
for sigma_c <= 80 km/s. We conclude that either the scatter of the v_c-sigma_c
relation is a function of v_c (and hence galaxy mass) or that the character of
the v_c-sigma_c relation changes at v_c ~ 80 km/s. Some inplications of our
findings are discussed.

Astrophysics