272 WHALES AND DOLPHINS 



and position of the teeth of considerable diagnostic value ; 

 especially in view of the fact that in so many species the 

 external form is very imperfectly known. In Hyperoodon a 

 pair of large teeth are to be found at the tip of the lower jaws, 

 usually concealed in the tissues of the gum, but in old speci- 

 mens sometimes with the points projecting. Those taken from 

 a stranded male Bottle-nosed Whale 26 feet long may be 

 regarded as typical ; they are conical, but expanding somewhat 

 at about half their length, then narrowing slightly to the lower 

 end. These teeth are about i\ inches in length at their widest 

 point, oval in cross-section, with the long axis about f inch and 

 the short axis about | inch. In adult females the teeth are 

 smaller, but with the same general characteristics. Occa- 

 sionally two pairs of teeth have been found in the lower jaws, 

 the second pair situated a little behind the first and of much 

 smaller size. Series of small vestigial teeth are also found 

 extending along upper and lower jaws, but completely concealed 

 in the gums. 



A feature serving to distinguish Hyperoodon from the 

 related genus Ziphius, with which it tends to be confused, is 

 the proportion that the distance from the tip of the snout to 

 blowhole length bears to the total length. Sir Sidney Harmer 

 has pointed out that in Ziphius the proportion expressed as a 

 percentage is from 10-4 to 12 '6, with an average of 11*46, 

 whilst in Hyperoodon it is from 14-0 to 22*0, with an average 

 of 17*46, the beak increasing in length with age. 



The Bottle-Nosed Whale, Hyperoodon rostratus, is an 

 abundantly occurring boreal species, and is common off the 

 British coast The specimens stranded on our shores, for the 

 most part in late autumn and winter, are believed to be 

 migrating individuals which, having spent the summer months 

 further to the north, are on the return journey southward. It 

 can be inferred from the distribution of stranded specimens 

 that, to quote Sir Sidney Harmer, " in the autumnal, southward 

 migration at least, the Bottle-nosed Whale is indifferent as to 

 the course it takes, since it has appeared in the North Sea and 

 the English Channel, in the Irish Sea and on the Atlantic coast 

 of Ireland " Old male animals rarely strand on the British 

 coast 



Females are believed to be more numerous than males and 



