PROP. W. H. PLOWEE ON THE GENUS MESOPLODON. 419 



& XV. The length of the animal is stated by Dr. Knox to have been 9 feet 3 inches. 

 The skuU is now in the British Museum. 



2. The skeleton of a perfectly adult animal, attributed by Dr. Hector to the same 

 species, prepared from a specimen cast ashore in Lyall Bay, and described by 

 Dr. Hector in Trans. New-Zeal. Inst. vol. vii. p. 262, 1875. This is also in the 

 British Museum i. 



3. The skeleton of an adolescent male M. grayi, stranded, with others, on the coast 

 near Saltwater Creek, about thirty miles north of Banks's Peninsula, New Zealand. 



4. The rostrum, mandible, and mandibular teeth of an old male animal, stranded 

 in December 1875 on the east coast of the North Island, attributed by Dr. v. Haast to 

 the same species. 



The last two were presented to the Museum of the Koyal College of Surgeons by 

 Dr. Julius V. Haast, F.R.S., of Christchurch, New Zealand. 



Of the specific distinction or identity of the 2nd, 3rd, and 4th I am not perfectly 

 satisfied, as the materials at hand are unfortunately not sufficiently complete for the 

 purpose of arriving at a definite conclusion. 



No. 3, though a perfect skeleton, is still immature. No. 2, though adult, is incom- 

 plete as regards the very important evidence furnished by the dentition. No. 4 is 

 only a fragment, and, although identified by Dr. v. Haast with his species M. grayi, 

 presents strongly marked differential characters which seem beyond the range of 

 individual variation. Under the circumstances, it is somewhat difficult to know what 

 course to pursue with reference to the names by which these specimens are to be 

 respectively distinguished ; but on the whole it will lead to less confusion if I designate 

 them, provisionally at least, by specific appellations, bearing in mind that it is quite 

 possible that further information and more abundant materials may cause a modi- 

 fication of this view. I shall therefore, in the present memoir, speak of the British- 

 Museum skeleton from Lyall Bay as M. australis, and the fragmentary skull from the 

 east coast of the North Island as M. haasti. 



Skull. — The skull of animals of the genus Mesojplodon is very easily distinguished 

 from those of the other Ziphioids by the characters previously given (T. Z. S. vol. viii. 

 p. 208)^. The ossification of the mesethmoid cartilage, and its coalescence with the 

 surrounding bones to form a solid rostrum, appear to be greatly dependent upon 

 the influence of age. It has not hitherto been found wanting in any thoroughly adult 

 example of any species of Mesoplodon or of Ziphms ; on the other hand, it appears 

 never to occur either in Hyperoodon or Berardius. 



' I am indebted to Dr. Giinther's kindness for facilities in examining and comparing these specimens, which 

 •were sent to the British Museum by Dr. Hector, F.E.S., of Wellington, New Zealand. 



" Almost simultaneously with my memoir appeared an excellent description of the skull of M. sowerhyi, com- 

 pared with that of Ziphius cavirostris, by Professor Turner (Transactions of the Eoyal Society of Edinburgh, 

 vol. ixvi.). 



