Mount Sabyinyo

Mount Sabyinyo ('Sabyinyo' is derived from the Kinyarwanda word 'Iryinyo', meaning tooth; also Sabinyo, Sabinio) is an extinct volcano in eastern Africa, in the Virunga Mountains. The summit of the mountain, at 3,645 metres (11,959 ft), marks the intersection of the borders of the Democratic Republic of the Congo, Rwanda, and Uganda. It also lies within the adjoining national parks established by these countries: Virunga National Park in the Congo, Volcanoes National Park in Rwanda, and Mgahinga Gorilla National Park in Uganda.
The slopes of Mt. Sabyinyo are a habitat for the Mountain Gorilla. The mountain carries the local nickname "Old Man's Teeth" because its serrated summit resembles worn teeth in a gumline (in contrast to the perfect conical summits of the adjacent mountains in this range).

Information based on http://en.wikipedia.org/wiki/Mount_Sabyinyo