The shoulder-blade is fan-shaped, with the external surface slightly concave, and its spinal border forming the segment of a circle : the two other borders are slightly concave and nearly equal ; the anterior is bifurcated, and thus presents two edges—one external, the other nearer the ribs. The external gives off a flat apophysis directed for wards, and enlarged at its extremity, which represents the acromion. The other border, which is the true anterior border, gives off also, but close to the articular surface, a flat apophysis, less than the acromion, descending a little and equally enlarged at the end : this is the corticoid process. The humerus is very short and stout. On the anterior part of its upper extremity or head is a tuberosity as large as itself : the lower head is enlarged and compressed from before backwards, and does not terminate in a facet that may be termed articular, but unites by synchondrosis with the radius and ulna : these two bones are short and compressed. The radius is in front and the largest, and its form is nearly rectangular : the ulna is behind and narrower. Its posterior border is concave, and it forma at its upper extremity a projecting angle, which is the only vestige of the olecranon. The carpal bones are flat, angular, and together form a sort of pave ment. There are three in the first row, the anterior of which responds to the radius; the posterior to the ulna, and the intermediate one to both radius and ulna. In the second row there are four, the anterior of which is the smallest. Under this anterior bone, which may be also taken for a metacarpal, is a nointed bone which is the sole vestige of a thumb. The next bone, which is the fore finger, is composed of nine joints, which must represent its metacarpal, its phalanges, and their epiphyses : there are seven in the third finger and four in the fourth ; the fifth is reduced to a single very small tubercle.
In the Narwhals the skull resembles that of the Dolphins, and especially the head of the Beluga, in structure; but instead of the numerous teeth ranged along the maxillaries presented by the Dol phins generally, there is but one on each side, directed forwards and implanted in an alveolus common to the maxillary and intermaxillary bones. Very rarely indeed are these teeth symmetrical ; and nearly always one of the two remains inclosed in its alveolus, whilst the other grows to a length of ten or twelve feet. The muzzle, and more especially the intermaxillary bones, are more widened than in the Dolphins. The intermaxillaries ascend near to the bones of the nose. The holes with which the maxillaries are pierced in their widened part, and which occupy the place of the suborbital holes, are large and numerous. The notch which separates this widened part from the muzzle is small, and the upper part of the orbit projects but little. The nasal are very small, and the left nostril is smaller than the other.
The number of vertebra, according to Scoresby, are-7 cervical, 12 dorsal, and 35 lumbar or caudal-54 in all. The spinal canal
is said to cease at the forty-first. The spinous apophyses begin to diminish at the thirty-fourth, and disappear at the thirty eighth. The V-shaped bones commence between the thirtieth and the thirty-first, and terminate between the forty-second and forty third. There are six pairs of true ribs and six false, all rather slender. The bones of the anterior extremity appear to bear a close resemblance to those of the Porpesse, except that the bones are more equal, as might be expected from the roundness of the Narwhal's flipper.
In the Hyperoodons the skull differs almost entirely in form from those belonging to the Dolphins. From the maxillaries, which are pointed in front and widened towards the base of the muzzle, rises on each of their lateral borders a large vertical crest, rounded above, descending obliquely forwards and more rapidly backwards, where it falls again nearly above the postorbital apophysis. Still more back wards, the maxillary bone, continuing to cover the frontal bone, ascends vertically with it and with the occipital, to form on the back part of the head a transverse occipital crest, which is very elevated and very thick, so that on the skull of the animal there are three of these great crests : the occipital crest behind, and the two maxillary crests on the sides, which are separated from the first by a wide and deep notch. They do not approximate above, nor do they form a vault, as in tho Dolphin of the Ganges, but simply a sort of lateral walls. The intermaxillaries, placed as ordinarily between the maxil laries, ascend with them to the nostrils, and passing by the side of them, raise themselves above, so that they take part in the formation of the posterior crest elevated upon the occiput. The two nasal bones, which, as well as the nostrils, are very unequal, are placed at the anterior surface of this occipital crest, and are raised to its summit. In other respects the connections of the bones are nearly the same as in the Dolphins.
The zygomatic apophysis of the temporal bone is thick, without being as long as in the Dolphin of the Ganges ; the orbit is as wide as in the ordinary Dolphins, and bounded in like manner below by a slender stern given off by the jugal bone. The parietal bones show themselves but very little in the temporal fossa, which is itself not much extended in height. Below, the palate is slightly carinated, indicating an approximation to the Balance. The lateral furrows observable in the common Dolphin are absent. The pterygoideans occupy a very great length in the back-nostrils, and much diminish the portion which the palatine bones fill in front. The vomer shows itself at two points of the lower surface, between the pterygoideans and the palatines, and between the maxillaries and intermaxillaries. The occiput is higher than it is wide. The lower jaw has not the symphysis longer than in the ordinary species of the Dolphins.