The only species which has ever been stranded on the shores of this country is _M. bidens_, an example of which was described many years ago as the "Toothless Whale of Havre"; it was an old animal which had probably lost its teeth. Nevertheless it received the separate generic and specific name of _Aodon dalei_. The animal lived for two days out of the water, and made a sound like the "lowing of a cow." An instance of the rarity of the Whales of this genus is afforded by _M. europaeus_, of which only a single skull is known; this was extracted from a dead body, found floating, about the year 1840. It has never appeared since. _M. layardi_ is remarkable on account of the very large size of its strap-shaped teeth; these curve over the upper jaw in such a way as to prevent the animal from fully opening its jaws. The case is curiously paralleled by the Sabre-toothed Tiger. This species is antarctic in range. From the opposite extremity of the globe comes _M. stejnegeri_, again known by but a single skull. It is singular on account of the large size of the brain case, and is a native of Bering's Straits. _M. hectori_ has its two teeth situated quite at the extremity of the mandible, and in this feature approximates to the genus _Berardius_. It was, indeed, confounded with that genus by one naturalist. {370} _Ziphius_ is a genus which is also of world-wide range. Here again the number of species is at present merely a matter of opinion. The prevalent impression, however, is that but a single species exists, which will therefore have the name of _Z. cavirostris_. The genus (and for the matter of that the species too) may be thus characterised in comparison with its allies. The mesethmoid is ossified as in _Mesoplodon_, but the nasals joined together form the vertex of the skull. There are two teeth near the symphysis of the mandible, besides the usual small and "functionless" teeth in the upper jaw. The vertebral formula is C 7, D 9 or 10, L 11, Ca 21.