In this paper all material of Chamaeleo quadricornis, present in museum collections, has been studied. Using morphological and geographical characteristics two subspecies are recognized, one of which is new: Chamaeleo quadricornis gracilior ssp. n. The history of the species has been reconstructed, using schemes of the orographic profile of West Cameroon, which furnishes a historical interpretation for the new subspecies. The closely related species C. eisentrauti and C. montium have also been discussed in this context. The assumed phylogenetic affinities are represented in a phylogram. This leads us to the following hypotheses: - in the Tchabal Mbabo mountains, which have hardly been explored faunistically, there probably lives a chameleon, that resembles C. quadricornis. - the differentiation in characteristics between C. montium and the sympatric C. eisentrauti and C. q. quadricornis (both being mutually allopatric) on the one hand and the allopatric C. q. gracilior ssp. n. on the other hand can be explained by "character displacement".