96 SPECIMENS OF CETACEA. 



mandibulai* symphysis. Only one species, Inia 

 qeoffrensis ; frequents the Amazon river. 



No specimen in Museum. 



III. PONTOPORIA. (Po.) 



Pontoporia, Gray, Zool. Erebus and Terror, 1846. 



Teeth most numerous, palatines separated by vomer, 

 sternum in two segments. Dorsal fin falcate. Only 

 one species, Pontoporia blainvilli ; frequents the Rio 

 Grande and the La Plata river. 



No specimen in Museum. 



Family III. DELPHINID.-E. 



(Dolphins.) 



Usually small, seldom exceeding 20 feet. Teeth usually 

 in both jaws, frequently numerous ; sternal ribs 

 ossified ; lachrymal conjoined with malar bone ; 

 pentadactylous. Skull not quite symmetrical. 



I. MONODON. (Mo.) 



Monodon, Linnceus, Syst. Nat., 1766. 



One tooth in superior maxilla of male, forming a 

 spirally twisted tusk, rarely two protruded teeth. 

 No dorsal fin. Manus short, narrow. Premaxillaj 

 convex in front of nares, broad and flattened in 

 beak. 



(1) Monodon monoceros. (Mo. m.) 



(Narwhal, Sea Unicorn.) 



Monodon monoceros, Linnceus, supra cit. 



Colour dark grey above, white below, marbled with 

 grey spots ; horn - like tusk several feet long, 

 spirally twisted. Head rounded, without distinct 

 beak. Length less than 16 feet. Vertebral formula 



C,D,,L,Cd.,, = 50. 



1. Skull, adult, 23^ inches long, greatest breadth 16 inches. 

 Beak 13^ inches long, 10^ inches broad at base. Pre- 



