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 Ziphioid grooves upon the throat. Nothing is known of the structure of the internal viscera of this Whale. It appears not to be really limited to the region of New Zealand, as is often stated, for Malm has lately described a skull (Berardius vegae) from Bering's Straits.

Mesoplodon is a world-wide genus embracing a number of species; on the lowest estimate seven species can be distinguished, and Sir W. Flower would add two more. These are moderate-sized Whales, 15 to 17 feet in length. In the skull the mesethmoid is ossified; the nasals are sunk between the upper ends of the premaxillae. There are but a single pair of teeth in the mandible attached to nearly the middle of its length (whence the generic name). The vertebral formula is C 7, D 9 or 10, L 10 or 11, Ca 19 or 20. The sternum consists of four or five pieces. The amount to which the cervical vertebrae are fused varies; but some are always fused.

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.