364 FOLLOW THE WHALE 



a result of its mention by Pliny. Then, in the Irrawaddy is found 

 Orcaella brevirostris, a true dolphin, while in China we have, first, 

 the pure-white Sotalia sinensis of the coastal waters which ascends 

 the larger rivers, and, second, the altogether different Lipotes vexilli- 

 feVy a true platanistid which dwells only in Tung Ting Lake, six 

 hundred miles up the Yangtze River in Hunan Province. 



The Irrawaddy dolphin and the Sotalias are true dolphins and be- 

 long to the family Delphinidae. They are most probably, if not as- 

 suredly, animals that originated in the sea and have returned to the 

 rivers in search of food and to escape enemies. Only the Cross River 

 dolphin, its stomach filled with vegetable food, is quite unique among 

 whales, and gives us pause to think. It is indeed odd that an animal 

 with millions of years on an animal diet behind it and anatomically 

 devised to live on such food should suddenly change its ways in a 

 river teeming with animal life, both great and small, as the writer 

 can personally attest. It is just possible that the Sotalias were devel- 

 oped in tropical rivers and then went to sea, while this species alone 

 remained behind. This does not, however, fit into the general pat- 

 tern displayed by almost all other whales and their fossil ancestors. 

 The Irrawaddy dolphin is another matter. This is very definitely a 

 marine type that has wandered up the river and its tributaries. It is 

 about seven feet long, dark slate gray in color, and has a blunt head 

 with bulbous forehead. There is a small, recurved dorsal fin, and the 

 flippers are pointed and slender. It eats fish, crayfish, and shellfish 

 and has about fifteen tiny teeth, less than a quarter of an inch long, on 

 either side of both upper and lower jaws. Altogether, it looks rather 

 like an unborn bottle-nosed whale. The remaining species are not 

 really dolphins, or Delphinidae, at all, but platanistids. To define 

 these is not easy. 



There is in this tiny group of little, geographically scattered, ap- 

 parently useless, retiring, and wholly inoffensive beasts an intrinsic 

 interest to the zoologist that might stand as an example to all think- 

 ing men. In their quiet, obscure way, puffing about in the muddy 

 shallows of their lukewarm streams and pools, they provide, for 

 any of us who would trouble to go and investigate them, an object 

 lesson in the art of living and a living demonstration of something so 

 incredibly ancient that its significance is not at first comprehensible. 



The little La Plata Pontoporia has never been known to exceed 



