1. Biology Department, Addis Ababa University, P. O. Box 1176, Addis Ababa, Ethiopia
2. Department of Animal and Human Biology, University of Rome ‘La Sapienza’, Via Borelli 50, Rome 00161, Italy
3. Queens College of the City University of New York, and American Museum of Natural History, Central Park West at 79th, New York, N.Y. 10024, USA
4. Carnegie Museum N. H., Museum Annex, 5800 Baum Boulevard, Pittsburg, PA 15206, USA