40 CETACEANS. 



parts of the Amazon, from its mouth to a distance of fifteen hundred miles in the 

 interior, one or other of the three kinds here mentioned are always heard rolling, 

 blowing, and snorting, especially at night, and these impressions contribute much 

 to the impression of sea- wide vastness and desolation which haunts the traveller." 



As the native inhabitants of Amazonia have a great objection to kill the 

 fresh- water dolphins, specimens are only procured with difficulty. 



THE AMAZONIAN DOLPHIN (A Hat. size). 



The La Plata The small La Plata dolphin (Stenodelphis blainvillei), from the 



Dolphin. estuary of the Rio de la Plata, differs from the preceding forms in the 

 presence of a well-marked back-fin and the extreme elongation of the jaws, which 

 carry from fifty to sixty teeth on each side. The blowhole, instead of forming a 

 longitudinal slit, is crescent-shaped and placed transversely. In the skeleton the 

 breastbone is long and composed of two distinct pieces. This species does not 

 attain a greater length than 5 feet, and in some respects serves to connect the other 

 members of the family with those of the one following. 



Allied Extinct The remains of a number of extinct dolphins have been discovered 



Dolphins. j n the Tertiary deposits of various parts of the world, which appear 

 more or less closely related to the existing members of this family. Among these, 

 two species from Argentina, respectively named Pontistes and Saurodelphis, 

 approach the living Stenodelphis ; while a third (Argyrodelphis) from Patagonia 

 is noteworthy from having the nasal bones well developed and roofing over the 

 hinder part of the nasal cavity in the manner characteristic of whalebone whales. 



