In the first two papers of this series, we derived and discussed the abundances of lithium in a sample of 161 galactic carbon stars. Here, we extend this sample to 203 stars and we present the spectra from which these abundances were derived, as well as a tabulation of the equivalent widths of the λ6708 Å feature. A comparison of our measurements with the equivalent widths from other authors is also made. Finally, we briefly discuss the possible variation in time of the lithium line in one star, R Lep.