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Show 1893.] CETACEAN GENUS MESOPLODON. 219 N. A cranium of an immature example of M. layardi in the Wellington Museum, N. Z.; sex unknown. 0. A cranium of a young individual of M. layardi, in the Napier Athenaeum, N . Z., in which the vomerine trough is quite empty and smooth ; sex unknown. P. A cranium of an aged individual in the British Museum, evidently a male. Q. For purposes of comparison with the species of Mesoplodon, I have examined the skeletons of Ziphius cavirostris ( = Epiodon chathamensis) in the Canterbury Museum, N . Z. R. A cranium of a very young individual of Ziphius 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 (Epiodon) chathamensis ( = Z. cavirostris) in the British Museum collection. T. A cranium of Ziphius cavirostris (the type) in the British Museum. IT. A younger cranium thanT, of Ziphius 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 angustus, M. gibbus, Choneziphius planirostris, and C. planus. For the opportunity of examining one or more of the above enumerated specimens I am greatly indebted to the kindness of Dr. Giinther, F.R.S., and Dr. Woodward, F.R.S., of the British Museum ; to Professor Stewart, P.L.S., Royal College of Surgeons, Prof. T. J. Parker, F.R.S., Dunedin, N . Z., Sir James Hector, F.R.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 conclusion that the species of Mesoplodon, and certainly some of Ziphius, 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 Mesoplodon hectori, Gray, by Hector and Haast, and Mesoplodon australis and Mesoplodon haasti by Sir W . Flower, are really more or less aged forms of Mesoplodon grayi, Haast. In his paper in the ' Transactions' of the Zoological Society already referred to, Sir W . Flower has been careful to remark :-" 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 |
