class="center">mm.

mm. mm. mm. mm. mm. mm. mm. mm. Total length ^b765+ 749 620 743± ... 733 740 660 ^c622 Length of rostrum ^b483+ 489 400 ... ... 485 500 410 ^c377 Tip of beak to end of pterygoid ^bd607+ 572 ... ... ... 582 590 517 ^cd466 Height from vertex to pterygoid 277 241 ... 254 267 272 258 235 248 Breadth between orbits ^e277 286 ^f254 267 292 293 253 ^f260 [278] Breadth between zygomatic processes 289 292 262 292 295 298 270 268 266 Breadth at maxillary notches 184 197 170 184 193 187 170 175 [166] Breadth of beak at middle 42 51 38 ... ... 36 46 ^g40 38 Depth of beak at middle 35 ... ^h31 ... ... ... ... ^h33 51 Greatest breadth of premaxillæ proximally 131 127 115 114 116 129 124 122 ... Greatest breadth of premaxillæ in front of anterior nares 107 102 ^h104 102 108 108 100 ^h76 92 Greatest breadth of anterior nares 54 ... 53 ... 53 50 50 50 39 Length of temporal fossæ 90 ... ... ... ... ... ^h66 82 Breadth between temporal fossæ 222 ... ... ... ... ... ... ... 208 Breadth of foramen magnum 50 ... ... ... 49 56 54 80 46 Length of mandible ^c651 ^ij470 543 ⁱ464 ... 639 640 560 ... Length of symphysis 237 241 162 ... ... 212 220 160 ... Greatest depth of mandible 106 114 92 102 116 110 97 95 ...

^a The size of the teeth makes it quite certain that it is an adult female.

^b End of beak broken off about 30 mm. from tip.

^c Right side. Add 31 mm. for breakage.

^d In median line.

^e At middle.

^f Between “suprafrontal processes of max.”

^g Grieg’s fig., p. 18, shows 44 mm.

^h From Grieg’s fig., p. 18.

ⁱ “Length of ramus.” Length of mandible=699 mm.

^j In Trans. Roy. Soc. Edinburgh, vol. 26, 1872, p. 776.

MESOPLODON DENSIROSTRIS (Blainville)?

Delphinus densirostris Blainville, Nouv. Dict. Hist. Nat., 2d ed., vol. 9, 1817, p. 178.

Ziphius seychellensis Gray, Zoöl. Erebus and Terror, 1846, p. 28.

The skull of the specimen from Annisquam, Mass., (Pl. 1, fig. 2) is, I regret to say, in rather poor condition. It is broken in the left orbital region, and all the bones, especially those of the beak, are warped by weathering. The proximal extremity of the left premaxilla is lacking and also the tip of the beak.

The skull is obviously that of a young animal, as all the sutures are open and the surface of the occipital condyles is pitted, owing to imperfect ossification.

Although the dimensions of the skull, with a few exceptions, agree well with those of young specimens of M. bidens, as shown by the foregoing table (p. 8), certain differences stand out conspicuously. The most salient of these is the depth of the beak as a whole and the depth and shape of the rostral portion of the premaxillæ. The latter portion of the premaxillæ instead of being low, with a straight inferior margin, is very high, with the inferior margin strongly convex. At the middle of the beak the premaxillæ are higher than the maxillæ on which they rest. It is true that the shape of the beak varies greatly with age in bidens and other species of Mesoplodon, but I do not find any evidence that such a change as is here indicated takes place in bidens. The form of the beak and of the rostral portion of the premaxillæ is that of M. densirostris.

The beak is almost as broad at the base as in bidens, but the lateral free margin of the maxilla anterior to the anteorbital notch instead of continuing along the side of the beak nearly to the tip, as in bidens, ends at a point