Hectok. — Xott's 0)1 the Whales of the New Zealaad Seas. 341 



Similar teeth in the gum of the upxaer jaw have, however, been 

 previously recorded for the closely- allied Ziphius cavirostris ; but, as 

 Professor Turner remarks iu describing a skull of this species found 

 in Shetland, " such teeth are quite rudimentary and functionless, and 

 the presence or absence of such aborted organs ought no more to form the 

 basis for establishing a specific difference, than should the entire absence 

 of teeth both in the upper and lower jaw of the Shetland cranium be a 

 reason for regarding it as a distinct species."* 



10. Mesoplodon layardi. 



DoUchodon layardi, Gray ; Cat. S. and W., 353 ; Hector, Tr. N.Z. Inst., V., 166. 

 Dolichodon traversi, Gray; Trans. N.Z. Inst., V., 96. 

 Mesoplodon layardi, Flower ; Nature, VII., 368. 

 Mesoplodon floweri, v. Haast ; Trans. N.Z. Inst., IX., 442. 



Only five or six examples of this curious and generally supposed 

 abnormal form of ziphioid have yet been met with, and of these I have seen 

 four, (1) a lower jaw from the Cape of Good Hope, collected by the Chal- 

 lenger Expedition, (2) a lower jaw I have already described from the 

 Chatham Islands,! (3) the complete skeleton in the Canterbury Museum, a 

 very complete anatomical description of which has been given by Dr. von 

 Haast,! and (4) the skeleton in the Sydney Museum, which has been made 

 the type of a new species, Mesojdodon giXntheri, Ea-efft, but which Professor 

 Flower considers to belong to the species now under review. § 



In the last specimen the teeth are not so fully developed into the wonderful 

 strap-shaped arches as in the type, but they are evidently intermediate in 

 then- form between it and the triangular tooth of M. sowerhyi. 'This skeleton 

 has not been yet described, I believe, but Mr. Scott states 1| that he has 

 compared it with the drawings of the skeleton of M. soxverhyi given by Van 

 Beneden and Gervais, and cannot detect any essential difference of structure 

 between them. The other species I have seen, although each has received 

 a different specific name, are only distinguished by a slight divergence in 

 the form of the mandible, and the manner in which the large abnormal 

 tooth or rather tusk has been bent or worn, which characters are obviously 

 due to individual variation. 



The skeleton described by Dr. von Haast is of a matm-e and probably 

 an aged animal, and as the other specimens that have large tusks corres- 

 pond in size, and the osteology in most points agrees with other Mesoplo- 

 donts, it is not improbable that it may be only the aged condition of some 

 species ah-eady known from immature individuals. Dr. von Haast states 



* Trans. Eoy. Soc. Edin., XXVI., 769. 

 t Trans. N.Z. Institute, V., 166. % Trans. N.Z. Inst., IX., Ai't. LV. 



§ Nature, VII., 368. || Mamm. Recent and Extinct, p. 116. 



