348 CETACEANS. 



lopment to a greater extent than those in the lower jaw of the 

 Hyperoodon ; but every other trace of teeth is soon lost. The 

 two persistent matrices rapidly elongate, but in the retrograde 

 direction, forming a long fang rather than a crown ; each tooth 

 sinks into a horizontal alveolus of the intermaxillary bone, or 

 rather at the junction of the intermaxillary with the maxillary, 

 and soon, by the forward growth of these bones becomes wholly 

 inclosed, like the germs of the teeth of the higher Mammalia at 

 their second stage of development. In the female Narwhal the 

 pulp is here exhausted, the cavity of the tooth is obliterated by 

 its ossification, further development ceases, and the two teeth 

 remain concealed, as abortive germs, in the substance of the jaws 

 for the rest of life ; so that in the skeleton a section of the skull 

 must be made in order to display them, as in Plate 87, fig. 2. In 

 the male Narwhal, the matrix of the tooth in the left intermaxillary 

 bone continues to enlarge ; fresh pulp-material is progressively added, 

 which by its calcification elongates the base and protrudes the apex 

 from the socket, and the tusk continues to grow, until it acquires 

 the length of nine or ten feet, with a basal diameter of four inches. 

 This is that famous so-called horn, which figures on the forehead 

 of the heraldic Unicorn, and so long excited the curiosity and con- 

 jectures of the older Naturalists, until Olaus Wormius made an end 

 of the speculative and fabulous ' monocerologies' by the discovery of 

 the true nature of their subject ; whilst Anderson(l) in the year 1736, 

 took advantage of the accident of the stranding of a Narwhal 

 at the mouth of the Elbe, to communicate to the Zoological 

 world, an accurate figure of the animal which bore the supposed 

 single horn. The exterior of this tusk is marked by spiral ridges, 

 which wind from within forwards, upwards, and to the left : 

 about fourteen inches of the tusk is implanted in the socket; it 

 tapers gradually from the base to the apex. The pulp-cavity is 

 continued nearly to the extreme point, but is of variable width ; 

 at the base it forms a short and wide cone, is then continued 

 forwards, as a narrow canal along the centre of the implanted 

 part of the tooth, beyond which, the cavity again expands to a 

 * Cited by Cuvier, Ossein. Foss. v, pt. 1. p. 319. 



