1. Department of Oral Anatomy I, School of Dentistry, Hokkaido University. Kita 13 Nishi 7 Kita-ku, Sapporo, Hokkaido 060, Japan
2. Wildlife Management Office. 1-18-18 Teraodai, Tama-ku, Kawasaki, Kanagawa 214, Japan
3. Division of Wild Animal Medicine, Nippon Veterinary and Animal Science University. 1-7-1 Kyonan-cho, Musashino, Tokyo 180, Japan