216 MK. H. O. FOBBES OX THE [Feb. 28, 



2. Observations on tlie Development of the Rostrum in the 

 Cetacean Genus Mesophdon, with Rema:rks on some of 

 the Species. By Heney O. Fobbes, F.Z.S., F.R.G.S. 



[Received January 17, 1893.] 

 (Plates XII.-XY.) 



In the course of my duties as Curator of the Canterbury 

 Museum, Christehurch, X. Z., I had occasion to study the Cetacea 

 in that collection. In my determinatiou of the species of Jleso- 

 2)hdon I was necessarily guided by the authoritative papers on this 

 group by Sir AVilliam Flower in the ' Transactions ' of this Society, 

 and by Sir William Turner in his Report on the Cetacea of the 

 ' Challenger ' Expedition. In his paper iu volume x. of our ' Trans- 

 actions,' page 422, Sir William Flower observes, in speaking 

 of a form near to Mesoplodon grayi, Haast : — " Making every 

 allowance for individual variation, it scarcely seems possible that 

 a rostrum such as that shown in figure 2 [i. e. Mesoplodon grayi : 

 Plate XIV. fig. 3] could change in the course of growth to that 

 in figure 3 [i. e. Mesoplodon haasti, Flower : Plate XII. fig. 2]. 

 If so, most of the determinations of the fossil species based solely 

 on the form of the rostrum are quite valueless." The same author, 

 on an earher page (page 420) of the same paper, remarks : — 

 " There is still much to be learued with regard to the mode of 

 ossification of this cartilage. All the specimens which I have had 

 an opportunity of examiuing are either so young that ossification 

 has not commenced, and the trough of the vomer in the rostrum 

 proper is completely empty in the dried skull, or so old that the 

 consohdation of the cartilage and its union with the surrounding 

 bone has been completed." In haxiug lived for some time in the 

 region in which this genus is not uncommon, I have been fortunate 

 inha\iiig had an opportunity of examining several immature crania 

 iu which the relations of the boues uhich constitute the rostrum 

 were such as to enable me to trace some unobserved stages in their 

 development. These observations I have thought of sufficient 

 interest to lay before the Society, especially as they bear on some 

 of the characters by which the vai-ious fonns of Mesoplodon and 

 Ziphius, both recent and fossil, have been separated from each 

 other. 



The deductions I have arrived at in this paper are based on a 

 personal examination and comparison of the following specimens : — 



A. A very young (and, according to Haast, a male) skuU, with 

 its mandible, — one of three specimens sent from the Chatham 

 Islands to Sir Julius von Haast in 1875. It is a co-type of Meso- 

 plodon (Oulodon) grayi, Haast, described in vol. ix. of the ' Transac- 

 tions ' of the Js.Ti. Institute. In this specimen the vomerine 

 trough is quite empty. It forms part of the coUsction in the Otago 

 Museum, Dunediu, X.Z. 



Ao. A young specimen in the Otago Museum, Dunedin, in 



