An efficient method of Identification of spectra on objective prim plates is described. 172 early-type stars of a region in Canis Major were classified in the MK system applying this method. Only 29 of them have been classified previously in this system by other authors, with good agreement in spite of different sources. A comparison with the HD spectral types in this sky region shows them to be, on the average, one spectral subclass later than the MK types assigned in this paper. %U http://sedici.unlp.edu.ar/handle/10915/76704Asociación Argentina de Astronomía