C 87 ] 



IV. Description of the Skeleton of Inia geoffrensis and of the Skull of Pontoporia 

 blainvillii, with Bemarks on the Systematic Position of these Animals in the Order 

 Cetacea. By William Henky Flower, F.RS., F.B.C.S., F.Z.S., d-c., Cmiservator 

 of the Museum of the Boyal College of Surgeons of England. 



Read November 22nd, 1866. 



[Plates XXV. to XXVIII.] 



I. On the Skeleton of Inia, geoSrensis. 



Of the several species of Cetaceans which are inhabitants of the waters of the 

 Amazon and its great tributaiy streams, one has particularly attracted the attention of 

 zoologists on account of certain peculiarities of its external conformation and of its 

 skull and teeth, the only parts of its stnicture hitherto described. 



The Inia, so called by M. Alcide d'Orbigny, from the name by which the animal is 

 known to one of the Indian tribes of Bolivia, is chiefly characterized hj the long, 

 narrow, and almost cylindrical rostrum, furnished with scattered, stout and crisp hairs, 

 by the broad, long, and obtuse pectoral fins, by the dorsal fin reduced to a mere ridge, 

 and especially by the develojiment of a large lobe on the inner side of all the posterior 

 teeth. 



The species is mentioned by Spix and Martins * as Delphinus amazonicus ; but for 

 the most complete account of its external characters, habits, and geographical distribu- 

 tion we are indebted to d'Orbigny, who described it under the name of Inia Miviensisf. 

 He also gives a fiigure of the animal, and a side view of a skull which he brought home 

 and deposited in the Museum at the Jardm des Plantes, with some details of the teeth. 

 I will quote from this memoir two observations — the first referring to the habits, the 

 second to the structure of this singular Cetacean : — " Toutes ces observations nous font 

 regarder cette espece comme ayant des mceurs beaucoup plus terrestres qu'aucune des 

 especes connues." — " Tons ces caracteres reunis a ule dorsale peu apparente, nous font 

 proposer la formation d'un nouveau genre, qui etablerait le passage entre les sousous 

 [Platanista'] et les stelleres " [Sii-eniaJ. 



* Keise in Brasil. t. iii. pp. 1119 & 1133 (1831). Von Martina States that his Deljyhinus amazonims agrees 

 very closely with Desmarest's description of D. geoffroyi, and even suggests that it may possibly belong to the 

 same species. His description of the teeth is sufSeient to determine the animal spoken of; but he says 

 " pinna dorsalis distincta, elata." Perhaps he has here confounded it with some of the other species of fresh- 

 water dolphins of the Amazon, the existence of which he did not suspect. The rude little figure he gives 

 (fig. 34) more resembles Delphinus fluviatilis (Gervais) of Castelnau's Voyage than the Inia. 



t Nouv. Ann. Mus. Paris, torn. iii. p. 23 (1 834). 

 VOL. VI. — PART III. 



