34.0 Tyidi^actluim. — -Zuoh'(i]j. 



able to give a fig'ure (plate XVII.) from a loliotograpli wliicLi I liad taken by 

 permission of Prof. Hutton. The other group, of wliich tbe type of M, 

 hectori is an extreme tliougli very young example, represents the forms 

 similar to M. euroixzus of the northern seas. 



These extreme forms are separated, but with many intermediate examples, 

 chiefly on account of the position and size of the tooth in the mandible, a 

 character to which I thinlc too much importance has been attached, as no 

 two specimens yet obtained agree perfectly in this respect. 



The complete skeleton of an adult male of M. hectori which I obtained 

 in Lyall Bay, near Wellington, in January, 1875,* agreed perfectly with 

 those parts which had been preserved by the late Dr. Knox of the type of 

 the species from Tetai Bay, Porirua Harbour, but in this second case the 

 teeth were situated several inches from the tip of the mandible, while in the 

 type they were at the extreme tip, though still lateral and not terminal as 

 in Zijiliius.^ 



Again, in the very young specimen of which I obtained only the lower 

 jaw from Kaikoura, the teeth were opposite the hinder edge of the 

 symphysis. I 



Dr. von Haast has lately described under a new genus Oulodon^ three 

 specimens obtained by Mr. Hood in the Chatham Islands of a Mesoplodon, 

 which has a row of small teeth in the upper jaw, in a position corres- 

 ponding to the shallow emargination of the upper part of the ramus of the 

 mandible of the Otago Museum skull («. fig. 1, pi. XVII). No anatomical 

 description of Ovhxhn has yet be m pubUshed, and as the characters of the 

 skulls figured and described by Er. von Haast were concealed by the dried 

 integument, its exact a£fi.nity to the other species of Mesoplodon cannot be 

 detected ; but, while the longest of the skulls (No. 1) has the mandible 

 X:)roduced to three times the width between the articulations (computed from 

 the orbital width which is given by Dr. von Haast) and the teeth at one- 

 third the length of the mandible from the tip, in both of wdiich characters 

 it again agrees with the Otago Museum skull, the shorter skull (No. 3) has 

 the length of the mandible only twice the articular width, and the tooth at 

 one-fourth the length of the mandible from the tip, thus approaching M. 

 hectori in its proportions. 



The presence of rudimentary teeth in the upper jaw of Mesoplodon is 

 certainly a most interesting discovery, but the animals have so seldom been 

 examined in the flesh that it may not prove to be of uncommon occurrence, 

 although it has escaped the notice of all naturalists prior to Dr. von Haast. 



* Trans. N.Z. Inst., VII., 262. f Trans. N.Z. Inst., in., pi. 14, 15. 



+ Trans. N.Z. Inst., VI., pi. 15a. § Trans. N.Z. Inst., IX., Art. LVI. 



