All figures about ⅕ nat. size. [Illustration: Plate 23 MANDIBLES OF ZIPHIUS CAVIROSTRIS] Mandibles of _Ziphius cavirostris_. Fig. 1. Bering Island. (Type of _Ziphius grebnitzkii_ Stejneger.) Cat. No. 20993, U.S.N.M. About ⅕ nat. size.