34^ WHALES AND DOLPHINS 



Genus Pontoporia (Stenodelphis). 



THE LA PLATA DOLPHIN (Pontoporia [Stenodelphis] , 

 blainvillei) . Fig. 97. 



The La Plata Dolphin is smaller than the two genera just 

 described ; it does not grow to a length of much more than 

 5 feet. In this creature the attenuation of the beak is greater 

 than in any other dolphin. Upper and lower jaws are armed 

 with finely pointed small teeth, between 50 and 60 in each 

 row. The forehead behind the beak is rounded and, as in 

 Inia, the blowhole is crescentic in outline. There is no depres- 

 sion between head and trunk. About midway along the back 

 is a conspicuous triangular dorsal fin. The flippers are broad 

 and bluntly rounded at the tip. 



In many respects Pontoporia is more specialized than other 

 Fresh-water Dolphins. In the articulation of the ribs, for 

 instance, only 3 or 4 pairs have a double-headed connection 

 with the backbone. 



The colour of this animal is palish brown and it occurs in 

 the estuary of the Rio de la Plata. 



Genus Lipotes. 



THE CHINESE RIVER DOLPHIN (Lipotes vexillifer). 

 PI. VII D. 



In 1918 Mr. G. S. Miller described a new species of River 

 Dolphin from the Tung Ting Lake, about 600 miles up the 

 Yangtze Kiang 



This dolphin, which grows to a length of 7 feet 6 inches, is 

 greyish or blue grey on the back and white on the belly. 



The beak, about 1 foot in length, is attenuated and curved 

 upwards. The blowhole, very asymmetrical and distinctly 

 on the left side, is situated just behind the crest of the 

 pronounced forehead. The dorsal fin, which is behind the 

 middle of the back, is bluntly triangular and the flippers are 

 broad and blunt at the free end. 



Teeth number 33 to 36 in each side of upper and lower jaws, 

 and the enamel is roughened much as in the Rough-toothed 

 Dolphin. 



