We have analyzed the energy-latitude dispersion of protons observed in the low-altitude dayside cusp on two orbits of the AE-C satellite in an attempt to reconstruct the velocity distribution of the source plasma. On the assumption that the source distribution has the form of a convecting bi-Maxwellian we have inferred the source values of V∥ (field-aligned flow velocity), T∥ (temperature parallel to the magnetic field) and (T∥/T⊥) n, where n is the number density. The inferred source parameters are consistent with a single-particle model of acceleration and injection through magnetic merging at the dayside magnetopause, provided that n is significantly smaller than the nominal fluid dynamic magnetosheath values and the ratio (T∥/T⊥) is significantly less than 1. Both of these conditions are expected as consequences of the magnetopause depletion layer effect described by Zwan and Wolf (1976) and Crooker and Siscoe (1977).