It is, when full grown, from thirteen to sixteen feet in length, exclusive of the tusk; and in circumference (two feet behind the fins, where it is thickest,) eight to nine feet. The form of the head, with the part of the body before the fins, is paraboloidal; of the middle of the body, nearly cylindrical; of the hinder-part, to within two or three feet of tail, somewhat conical, and from thence a ridge, commencing both at the back and belly; the section becomes first an ellipse, and then a rhombus, at the junction of the tail. At the distance of twelve or fourteen inches from the tail the perpendicular diameter is about twelve inches, the transverse diameter about seven. The head is about one-seventh of the whole length of the animal; it is small, blunt, round, and of a paraboloidal form. The mouth is small and not capable of much extension. The under-lip is wedge-shaped. The eyes are small, the largest diameter being only an inch, and are placed in a line with the opening of the mouth about thirteen inches from the snout. The blow-hole, which is directly over the eyes, is a single opening, of a semicircular form, about three and a half inches in diameter, or breadth, and one and a half radius, or length. The fins are twelve or fourteen inches long, and six or eight broad; the tail, from fifteen to twenty inches long, and three to four feet broad. It has no dorsal fin, but in place of it an irregular, sharpish, fatty ridge. The colour of the narwal is in the young animal blackish grey, on the back variegated with numerous darker spots, running into one another; in the older animals the ground is wholly white, or yellowish white. The integuments are similar to those of the mysticetus, only thinner.