The large scale trend of rotation curves in the spiral galaxies NGC 1068 and 3310.

We present a dynamical study of the bright spiral galaxies NGC 1068 and NGC 3310. Our purpose is to extend our knowledge of the rotation curves for these systems to radii as large as 10 kpc from the center in the light of the suggestion that galaxies might be surrounded by massive halos with high M/L ratios. From our curves no outer decrease in the velocity is evident, but a slight increase of the velocity is found, yielding a mass around a few tens of billions of solar masses for the galaxies. The inner M/L ratios within 7 kpc are quite low, with maximum values between five and seven solar masses/solar luminosities. The presence of a significant quantity of matter in the external parts of these galaxies, indicated by the observed velocity trends, cannot yet be interpreted as halos as massive as those required in dynamical models, at least within the radii explored.