In many characters, this species resembles the physalis, though, I think, with an essential difference. The musculus is shorter, having a larger head and mouth, and a rounder under-jaw than the physalis and is said to feed principally upon herrings. Several individuals, apparently of this kind, have been stranded or killed on different parts of the coast of the United Kingdom. One was embayed and killed in Balta Sound, Shetland, in the winter of 1817-18, some remains of which I saw. It was eighty-two feet in length, the jaw-bones were twenty-one feet long, and the largest lamina of whalebone about three feet. Instead of hair at the inner edge, and at the point of each blade of whalebone, it had a fringe of bristly fibres, and it was stiffer, harder, and more horny in its texture than common whalebone. It produced only about five tons of oil, all of it of an inferior quality; some of it viscid and bad. It valued, deducting expenses, no more than £60 sterling. It had the usual sulci about the thorax, and a dorsal fin. A smaller species of whale is _Balænoptera jubartes_ of La Cepède, _Balæna boops_ of Linnæus, or the finner of the whale-fishers. The following is its description:—Length, about forty-six feet; greatest circumference of the body, about twenty feet; dorsal protuberance, or fin, about two feet and a half high; pectoral fins, four or five feet long externally, and scarcely a foot broad; tail, about three feet deep and ten broad; whalebone, about three hundred laminæ on each side, the longest about eighteen inches in length, the under-jaw about fifteen feet long, or one-third of the whole length of the animal; sulci, about two dozen in number; two external blow-holes; blubber on the body two or three inches thick, under the sulci none. The last, and smallest of the whalebone whales, with which I am acquainted, is the _Balænoptera acuto-rostrata_ of La Cepède, _Balæna rostrata_ of Linnæus, or the beaked whale. An animal of this kind was killed in Scalpa Bay, November 14, 1808. Its length was seventeen and a half feet, circumference twenty. Pectoral fins, two feet long and seven inches broad; dorsal fin fifteen inches long by four and a half feet broad. Largest whalebone, about six inches. The rostrata is said to inhabit principally the Norwegian Seas, and to grow to the length of twenty-five feet. One of the species was killed near Spitzbergen, in 1813, and I have some of the whalebone in my possession. Three species of narwals are noticed by La Cepède, though I myself have seen but one, and perhaps the other species are imaginary, for the animal varies in appearance. It is the _Monodon monoceros_ of Linnæus, and the narwal, or unicorn, of whalers.