This very meagre series of differential characters is largely due to _Pontoporia_ on the Platanistid side, and to _Monodon_ and _Delphinapterus_ upon the Delphinid side. Otherwise the family Platanistidae would be extremely distinct. The two last-named genera have separate cervical vertebrae, and in the Beluga at any rate this is expressed externally by a quite distinct neck. Moreover, as Mr. True has pointed out, the pterygoid bones have not the involuted cavity below which characterises other Dolphins; and they have, what other Dolphins have not, an articulation outwards with the roofing bones of the skull. Sir W. Flower described the fact that in Inia (and the same occurs in Pontoporia) the palatines are separated from each other by the intervention of the vomer. In this feature they resemble certain Ziphioids, _Berardius_, _Oulodon_ (= _Mesoplodon_) _grayi_, and _Hyperoodon_. The true Dolphins also appear to show the same intervention of the vomer in a few cases. There is nothing, therefore, distinctive from the Delphinidae in this feature. The existence of cartilaginous sternal ribs in _Inia_ and _Platanista_ shows affinity between these two genera and the Physeteridae. _Pontoporia_ is Dolphin-like in this particular, as it is also in the mode of articulation of the ribs with the vertebral column. But this last matter has already been dealt with. The principal reason for placing _Pontoporia_ with the other two genera is the close resemblance which its skull bears to that of _Inia_. The first genus of this family which will be noticed is _Platanista_. {381} The following are its main characters:--Dorsal fin absent. Eyes rudimentary. Pectoral fins large and truncated at the extremity. Teeth, about twenty-nine in each half of each jaw. Scapula with the acromion coinciding with its anterior edge. Skull with enormous maxillary crests, and with the palatines entirely concealed by the pterygoids. The length of the above definition will serve to indicate how anomalous in many particulars is the structure of this "Dolphin." There is apparently but one species, _P. gangetica_, the "Susu." The Indian vernacular name is derived from the sound that the animal makes when spouting. It is an inhabitant of the Ganges and the Indus, together with their tributaries, and ascends very high up its streams. It is also thought to be purely fluviatile and never to desert the rivers for the sea. _Platanista_ lives chiefly by grubbing in the mud for prawns and fish. Grains of rice have also been found in the stomach, but this would seem to be accidental. The long snout of the Susu has been compared to the long snout of the Gharial, a native of the same region. This Whale grows to a length of over 9 feet, but this length is exceptional. Its anatomy has been elaborately described by Dr. Anderson.[262]