500 CETACEA. 



Platanist in which the ribs are attached direct to the bodies of the vertebrae in 

 the sixth, seventh, eighth and ninth vertebrae, owing to the entire absence of any 

 intervening process or projection from the bodies of these vertebrse, and owing 

 perhaps to the imperfectly developed character of the transverse processes, the latter 

 appear suddenly to cease, whereas in the adult the transverse processes appear gra- 

 dually to subside on to the bodies of the vertebrae and to exist as tolerably well 

 marked short processes even on the eighth and ninth vertebrae on which in the 

 young there is no trace whatever of such a process, the structures afterwards deve- 

 loped in these as in the seventh also being only outgrowths of the bodies of the 

 vertebrae. The process bearing the tenth rib is entirely different, and is a distinct 

 structure developed quite independently from a centre of its own. These processes 

 are apparently developed from behind forwards, as in a young skeleton those of the 

 caudal and posterior portion of the lumbar region are firmly united to their vertebra, 

 while those bearing ribs and a few behind them are not so united to their segments. 

 Flatanista in having eight lumbar vertebrae more resembles Fontoporia than 

 Inia, as the former, according to Burmeister, has six or seven' lumbar vertebrae, 

 whereas Inia is stated by Elower to have only three or four, which is a marked 



difference from what prevails in the ordinary JDelphimdcB, in which the lumbar region 

 has great extension. 



Professor Elower remarks that " nothing can be more dissimilar than the lumbo- 

 caudal region of the special column in Inia and Flatanista,'' and from Burmeister's 

 researches on the anatomy of Fontoporia we may add, between this dolphin and 

 the Gangetic form. 



In Flatanista, as I point out hereafter, the sternal ribs, although cartilaginous 

 in youth, become ossified with adult life, but always with a small portion of carti- 

 lage or ' intermediate rib,' as in the Monotremes, intervening between the end of the 

 rib and the ossified sternal rib, whereas in Inia the sternal ribs are always cartilagin- 

 ous. Flower in grouping Flatanista, Inia and Fontoporia with Fhyseter, Hyperoodon 

 and the Ziphioids did so under the impression that the absence of ossified sternal ribs 

 w^as a character common to them as a group. But now, in addition to the sternal 

 ribs of Flatanista being known to be ossified in adult life, Burmeister^ has shown 

 that the sternal ribs of Fontoporia are ossified, as in marine dolphins generally, to 

 which it is allied. 



Such facts have an important bearing, as Professor Elower ^Nho\^ facile princeps 

 in this department of anatomy, when seeking for some starting-point or basis for a 

 primary division of the toothed whales, Odontoceti, selected this presence or absence of 

 ossified sternal ribs as " a character derived from a part of the organization apparently 

 less liable to adaptive modifications than the teeth or fins." It would now appear 

 however, that this character has not that reliability w^hich it was thouo"ht might be 

 attached to it. The facts already adduced, and those yet to follow in this contribu- 

 tion to the anatomy of Flatanista, seem to me to confirm the just appreciation which 



1 Proc. Zool. Soc, 1867, p. 485. 

 ^ Loc. cit.,p. 412. 



