1893.] CETACEAN GENUS MESOPLODON. 219 



N. A cranium of an immature example of M. layardi in the 

 Wellington Museum, N. Z. ; sex unknown. 



O. A cranium of a young individual of M. layardi, in the Napier 

 Athen?eum, N. Z., in which the vomerine trough is quite empt}^ 

 and smooth ; sex unknown. 



P. A cranium of an aged individual in the British Museum, 

 evidently a male. 



Q. Por purposes of comparison with the species of Mesoplodon, 

 I have examined the skeletons of Zipliius cavirostris {■=Epiodon 

 Chatham ensis) in the Canterbury Museum, N. Z. 



E. A cranium of a very youug individual of Ziphins cavirostris, 

 collected by myself in the Chatham Islands in January last (1892), 

 and now in the Canterbury Museum, in which the vomerine spout 

 is quite empty and smooth, except on the bottom of the trough, 

 where there is a small upgrowth. 



S. A skeleton of Ziphius {Epiodoii) chathamensis { = Z. cavirostris) 

 in the British Museum collection. 



T. A cranium of Zijihi^is cavirostris (the type) in the British 

 Museum. 



U. A younger cranium than T, of ZipMus cavirostris, in the same 

 collection. 



V. A skeleton and two crania of Berardius arnuxii, in the 

 Canterbury Museum, N. Z. 



With these I have also compared the various fossil species in 

 the Geological Department of the British Museum, Mesoplodon 

 angustiis, M. r/ihbus, Choneziphius pdanirostris, and C. planus. 



Por the opportunity of examining one or more of the above 

 enumerated specimens I am greatly indebted to the kindness of 

 Dr. Giinther, F.K.S., and Dr. Woodward, T.R.S., of the British 

 Museum ; to Professor Stewart, P.L.S., Eoyal College of Surgeons, 

 Prof. T. J. Parker, P.E.S., Dunedin, N. Z., Sir James Hector, 

 P.E.S., Wellington, N. Z., and to the authorities of the Hawke's 

 Bay Philosophical Society in Napier, N. Z. 



From an examination of these specimens I have come to the 

 conclusicm that the species of Mesoplodon, and certainly some of 

 Zipjlmis, change very greatly in regard to the form of their rostra 

 with age and sex ; and from the transverse sections of various rostra 

 that I exhibit it will be apparent that the contour of each varies 

 with the amount of ossification and consolidation of the rostral 

 bones in different sexes at different ages. It will then be seen, I 

 think, that the species designated JMesoplodon hectori, Gray, by 

 Hector and Haast, and Mesoplodon axistraJis and Mesophdon haasti 

 by Sir W. Flower, are really more or less aged forms of Mesoplodon 

 ijrayi, Haast. In his paper in the 'Transactions' of the Zoolo- 

 gical Society already referred to. Sir W. Flower has been careful 

 to remark : — " Under the circumstances it is somewhat difficult to 

 know what course to ])ursue with reference to the names by which 

 these specimens are to be respectively distinguished ; but on the 

 whole it \\W\ lead to less confusion if 1 designate them, provi- 

 sionally at least, by specific appellations, bearing in mind that it 



