Hon. W. Rothschild on Mesoplodon bidens. 439 



eacli from a common source, New Guinea. Thirdly, that 

 New Zealand and New Caledonia were early separated from 

 the northern archipelagoes, and ceased to receive overland 

 immigrants therefrom. Fourthly, that tlic Fiji.s remained to 

 a later date in communication with the Solomons, but were 

 severed from that group before the latter had acquired from 

 Papua much of its present fauna. 



LXXI. — Note on Mesoplodon bidens. 



To the Editors of the ^Annals and Magazine of 

 Natural llislory.^ 



Gentlemen, — Although I do not pretend to have any special 

 knowledge of Cetacea, I think it might prove of some interest 

 to your readers, and also serve to complete the account given 

 in the April number of your Journal of this extremely rare 

 whale, if I draw attention to a fact which has come to light 

 since the skeleton of tiie foetus described has been macerated. 



In Messrs. Southwell and Harmer's account of Mesoplodon 

 bidens the authors say that while several of the older drawings 

 and descriptions give the colour of the ventral surface as 

 white, in the tine adult female I now possess the whole ventral 

 surface is black. 



Now in the mandible of the foetus the two teeth charac- 

 teristic of the male are much developed and nearly 1^ inch 

 long, which seems to prove this foetus to have been of the 

 male sex. In the foetus the under surface, although much 

 suffused with blood, clearly was white ; this, I think, tends 

 to prove that the male Mesoplodon bidens has the ventral 

 surface white, while the female, apart from the white spots on 

 the back, is uniformly dark on both ventral and dorsal 

 surfaces. 



I remain. Gentlemen, 



Yours faitlifuUy, 



WaLTEK R01HSCH1I.D. 



