  We measure the shape of the velocity ellipsoid in two late-type spiral
galaxies (Hubble types Sc and Scd) and combine these results with our previous
analyses of six early-type spirals (Sa to Sbc) to probe the relation between
galaxy morphology and the ratio of the vertical and radial dispersions. We
confirm at much higher significance (99.9 percent) our prior detection of a
tight correlation between these quantities. We explore the trends of the
magnitude and shape of the velocity ellipsoid axes with galaxy properties
(colour, gas surface mass density, and spiral arm structure). The observed
relationships allow for an observational identification of the radial and
vertical disk heating agents in external disk galaxies.
