304 A BOOK OF WHALES 



the species were founded, to be white with a black 

 dorsal band. D'Orbigny described another dolphin 

 which he thought, but without any evidence, to be 

 the same species ; as this evidence is wanting it 

 will be unnecessary to repeat his description. Mr. 

 Lyclekker, on the other hand, has described it as a 

 palish brown, harmonising with the brown-coloured 

 water of the estuary of the Amazons and the Rio de 

 la Plata. 



EXTINCT PLATANISTIDS 



More generic types have been described as be- 

 longing to this group of the Cetacea than to any 

 other. And it is furthermore remarkable as being 

 the only existing group that goes back to the far 

 past of the Eocene period ; indeed, apart from the 

 Zeuglodonts these whales are the only ones that have 

 so ancient a history. But, as is so often the case, 

 their remains are for the most part fragmentary, and 

 not much of great importance has been or apparently 

 can be deduced from their study. The restricted 

 range of the existing Platanistidae is in interesting 

 harmony with the great antiquity of the race ; it is 

 so often the case that a rapidly dwindling group of 

 animals consists of existing forms which occupy very 

 limited areas ; it is as if the long continuance of the 

 types in question had rendered them partially effete 

 and unable to cope with changed conditions and new 

 forms allied to themselves ; in order to survive they 

 have had to creep into corners where the tide of 



