220 A BOOK OR WHALES 



Mesoplodon layardi, Gray* (with synonyms : 

 Callidon guntheri, Gray ; Dolichodon traversii, Gray ; 

 Mesoplodon floweri) Haast), is provided with a rostrum, 

 narrow at base ; basirostral grooves present ; two 

 foramina of fifth nerve on a level. Tooth very large, 

 near hinder edge of mandibular symphysis. 



This Mesoplodon is remarkable on account of the 

 singular growth of the strap-shaped teeth. These 

 finally grow round the jaw so as to prevent their 

 opening to the full extent. At first this singular 

 arrangement was naturally regarded as an abnormality, 

 but later it was found to characterise the species, 

 which is in this peculiar feature of its organisation 

 comparable to the sabre-toothed tiger. It is, like the 

 last, a southern species. 



Mesoplodon kectori, Gray ;f ( = Berardius arnuxi, 

 Hector; Mesoplodon knoxi, Hector). In this species 

 the rostrum is broad at the base ; the basirostral 

 grooves are absent ; foramina of fifth nerve on a 

 level. Tooth close to apex of mandible. 



Of this species Sir W. Flower wrote that "it does 

 certainly present some transitional characters (between 

 Mesoplodoii and Berardius] ; but as it is only known 

 by the skull of a very young animal it is scarcely 

 safe to decide its position, except provisionally." It 

 is, of course, the apical position of the mandibular 

 teeth that has led to its confusion with Berardius. 



* Free. Zuol. ..W., 1865, p. 358. 



t Ann. and Mag. Nat. hist. (4), viii., p. 115. 



