216 MR. H. O. FORBES 0>' THE [Feb. 28, 



2. Observations on the Development of the Rostrum in the 

 Cetacean Genus Mesoplodon, with Remarks on some of 

 the Species. By Henry O. Forbes, F.Z.S., F.R.G.S. 



[Eeceived January 17, 1803.] 

 (Plates XII.-XY.) 



lu the course of my duties as Curator of the Canterbury 

 Museum, ChristC'hurch, X. Z., I had occasiou to study the Cetacea 

 in that collection. In my deteriniuatiou of the species of Meso- 

 plodon I was uecessarily guided by the authoritative papers ou this 

 group by Sir William Flo\\er in the ' Transactions ' of this Society, 

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

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

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

 of a form near to Mesoplodon f/rai/i, 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, Flo^^■er : Plate XII. fig. 2]. 

 If so, most of the determinations of the fossil s^jecies based solely 

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

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

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

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

 an op])ortuuity of examining 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 

 consolidation of the cartilage aud its union with the surrounding 

 boue has been completed." In having lived for some time in the 

 region in ^^■hich this geuus is uot uncommon, I have been fortunate 

 in having had an opportunity of examining several immature crania 

 in which the relations of the bones which constitute the rostrum 

 were such as to enable me to trace some uuobsersed 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 various forms of Mesoplodon and 

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

 other. 



The deductions I have arrived at iu this paper ar^ based on a 

 personal examination and comparison of the following specimens : — 



A. A very young (aud, according to Haast, a male) skull, with 

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

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

 plodon (Otdodon) [/rai/i, Haast, desci'ibed in vol. ix. of the ' Transac- 

 tions ' of the N.Z. Institute. In this specimen the vomerine 

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

 Museum, Duncdin, X.Z. 



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



