1. Department of Zoology, National Science Museum, Tokyo, Shinjuku-ku, Tokyo 169-0073, Japan
2. Kanagawa Prefectural Museum of Natural History, Odawara-shi, Kanagawa 250-0031, Japan
3. Animal Medical Center, College of Bioresource Sciences, Nihon University, Fujisawa-shi, Kanagawa 252-8510, Japan
4. Laboratory of Veterinary Surgery, College of Bioresource Sciences, Nihon University, Fujisawa-shi, Kanagawa 252-8510, Japan
5. Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa-shi, Kanagawa 252-8510, Japan