66 

 TamUy II. PONTOPORIAD^.' 



With dorsal fin ; head small, convex, longly-beaked ; jaws nearly of the 

 same length and breadth, armed throughout with teeth ; skull, long- 

 beaked ; beak slender, compressed, about three-fourths of the entire 

 length of skull ; mandibular symphysis very long, upwards of half of 

 the entire length of ramus, greatly resembling those of Platamsta and 

 Inia; costo-sternal ribs ossified ; cervical vertebrae free; teeth numerous, 

 permanent, conical. 



Genus Pontopoeia,' Q-ray. 



Beak high, compressed, slender smooth ; pectoral fin short, truncated, 

 five-fingered ; dorsal fin short, triangular ; mandible grooved on each 

 side ; symphysis frequently anchylosed by age ; teeth with a swollen 

 ring round the base. 



PoNTOPOEiA BiiAiBTiLLn, TreminviUe. The Pontoporia. 



Synonyms — Delpliinus SlainviUii, Tremin. 



StenodelpMs SlainviUii, Gervais. 



Fontoporia Blainvillii, Gray, S. and "W. p. 231 ; Suppl. 

 p. 96 ; Flower, Trans. Zool. Soc, vol. 6, p. 87. 



Teeth 1^ to U^:=212 to 222, small, in many respects resembling those 



of the Inia. 



Inhab. coasts of Buenos Ayres — South Atlantic. 



Por many years a doubt has existed whether this species was fluvia- 

 tile or marine, and whether it possessed a dorsal fin or was deprived of 

 • that appendage ; for only a few remains, of uncertain origin, were known 

 to the scientific world. Dr. Burmeister of Buenos Ayres has recently 

 solved the problem, by the issue of a valuable monograph, whereby not 

 only all doubts of its structure and habits are removed, but its position 

 in the cetacean group is so far defined that it cannot be retained among 

 the Platanistidte, where some eminent writers had placed it, neither can 

 it be classed with the Delphinidse proprise, as determined by other 

 zoologists : the only alternative therefore appears to be to form an 

 express family for its reception, and possibly for other alUed kinds, 

 recent or fossil, which some day may be brought to light. 



It apparently constitutes an excellent connecting link between the 

 fresh-water and marine dolphins, approaching the former by the pro- 

 longed beak, the greatly lengthened symphysis, and the free condition 

 of the cervical vertebrs ; and to the latter, by the dorsal fin and ossified 

 cartilages of the ribs. I, therefore, assign to it the present position. 



' it6vtos, the sea, and Tr6pts, a calf. 



