  In their paper published in 1997, Richmond and Richmond classified metric
spaces in which all triangles are degenerate. That result was later reproved by
Dovgoshei and Dordovskii in the finite case and it was generalized to finite
pseudometric betweennesses by Beaudou et al. In this paper, we give a new,
independent proof to the finite case of the original theorem which we
reformulate in terms of linearity of betweenness structures.
