pT sy a. 
IV. Description of the Skeleton of Inia geoffrensis and of the Skull of Pontoporia 
blainvillii, with Remarks on the Systematic Position of these Animals in the Order 
Ceracea. By Witiiam Henry Fiower, F.RS., FRCS, F.Z.S8., &c., Conservator 
of the Museum of the Royal College of' Surgeons of England. 
Read November 22nd, 1866, 
[Puates XXV. to XXVIII] 
I. On the Skeleton of Inia geoffrensis. 
Or the several species of Cetaceans which are inhabitants of the waters of the 
Amazon and its great tributary 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 structure hitherto described. 
The Jnia, 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 by 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 development of a large lobe on the inner side of all the posterior 
teeth. 
The species is mentioned by Spix and Martius* 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 boliviensist. 
He also gives a figure of the animal, and a side view of a skull which he brought home 
and deposited in the Museum at the Jardin 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 espéce comme ayant des mceurs beaucoup plus terrestres qu’aucune des 
espéces connues.”—- Tous ces caractéres réunis a uhe dorsale peu apparente, nous font 
proposer la formation d’un nouveau genre, qui etablerait le passage entre les sousous 
[ Platanista| et les stelléres” [Sirenia). 
* Reise in Brasil. t. iii. pp. 1119 & 1183 (1831). Von Martius states that his Delphinus amazonicus 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 sufficient 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. 
+ Nouy. Ann. Mus. Paris, tom, iil. p. 23 (1834). 
VOL. Vi.—PART III. 0 
