_83991. Bering Island._—Similar in all respects to preceding, but mesirostral ossification a little less well developed. _22874. Bering Island._—Entirely similar to two preceding, but premaxillæ a little curved out from mesirostral ossification and left premaxilla opposite maxillary notch rather strongly inclined, nearly vertical. Anterior face of nasal boss distinctly concave. (Skull defective.) _21246. Bering Island._—Sutures as in three preceding skulls. Mesirostral ossification distinct and rounded, but much below level of premaxillæ. Rostral portion of premaxillæ narrow and widely divergent toward base of rostrum, leaving mesirostral entirely exposed. Right premaxilla on a line with maxillary notches strongly concave and sunk below level of maxillæ. Left premaxilla vertical, with a broad groove. Right premaxilla remains low and concave proximally, the posterior end being then abruptly turned upward and reaching level of vertex. Orifice of anterior nares on a level with lower end of nasal boss, and vomer resting against anterior face of nasals, which latter have a median ridge continuing nasal septum, but with a slight vacuity between the two. Rudimentary alveolar groove nearly obliterated. Outer sides of premaxillæ at distal end strongly concave. Rostrum rather acute, about as deep as wide opposite distal ends of maxillæ. (Pl. 15, fig. 2.) _20993. Bering Island._—Adult male? (Type of _Z. grebnitzkii_). Majority of sutures open, but maxillæ and premaxillæ anchylosed together above and on the sides. Premaxillæ approximated anteriorly, but diverging posteriorly. Mesirostral ossification well developed, reaching level of premaxillæ; anteriorly rather narrow but a little broader near middle of rostrum, where it is beveled off abruptly. Behind this point premaxillæ strongly concave, nearly vertical and widely separated, forming a large and deep basin, in the bottom of which the vomer appears as a broad, irregular bony surface. Bottom of basin much below level of surrounding parts. Orifice of anterior nares much below level of nasal boss. Vomer reaching lower end of nasals. Anterior face of latter strongly concave, with only a moderate median ridge completing nasal septum above. Mesirostral with a median groove at distal end. Premaxillæ high at distal end, but sides nearly plane. Rostrum compressed near apex, deeper than wide. (Pl. 16, fig. 1; pl. 19, fig. 1; pl. 20, fig. 3.) Rami of mandible anchylosed together and suture partly obliterated. Teeth conical, with rather short, acute tips; roots closed, short and conical; diameter, 25 mm. (Pl. 23, fig. 1; pl. 24, fig. 2.)