92 MB. W. H. FLOWER ON THE OSTEOLOGY OF 



broad and -25" high, distinctly separated by a suture from the frontals. It will be seen 

 from the above description that the nasals are extremely different from those of most of 

 the Delphinidce, in which they are generally reduced to irregular, oval, unsymmetrical 

 nodules. Phoccena, however, differs from its allies in this respect, and closely approxi- 

 mates to Inia. In Flatanisfa also the nasal bones are well-developed flattened plates ; 

 but they partake of the great elongation, narrowness, and latei-al distortion which per- 

 vades this region of the skull. 



The opening formed by the junction of the anterior nares is 1" long, and the same 

 width posteriorly. It is bounded laterally and in front by two very prominent, rounded, 

 longitudinal elevations, formed by a thickening of the premaxillaries, like that seen in 

 this region in Phocwita and Beluga, but considerably more mai'ked. No part of the 

 maxillaries comes to the surface in the middle line in front of the narial aperture as in 

 many of the Delj)himd(e (e. g. Olobiocephahis). 



The rostrum is exceedingly long and narrow, and, except at its base, much compressed. 

 The diminution of its breadth takes place rapidly for the first fourth of its length, but 

 for the remaining portion only very gradually. The bone of which it is composed is of 

 dense texture ; and, even in this young subject, the sutures between the premaxillaries 

 and maxillaries are almost obliterated. The width of the premaxillaries scarcely alters 

 through their entire length, their outer boundaries being parallel, and the general 

 diminution in the breadth of the rostrum taking place solely at the expense of the 

 maxillaries. There is a narrow interval throughout in the middle line between the 

 premaxillaries, and the subjacent cavity for the median ethmoid cartilage is not filled up 

 with bone as in many of the Ziphiinw. 



On each side of the inferior surface of the rostrum (Plate XXVI. fig. 1) the alveolar 

 tract, marked by the row of deep and distinctly separated tooth-sockets, extends from 

 the apex to 1^" from the bottom of the antorbital notch. Between these tracts the 

 palatine surface is quite flat, and in the anterior three-fourths slightly raised above 

 their level. At the middle of the rostrum it is only -4" wide, but gradually expands 

 posteriorly. Between the two maxillary bones, in the median line is a narrow fissure, 

 in which, 1" behind the middle of the rostrum, a thin strip of the vomer appears, and 

 continues visible as far as the posterior edge of the palate. 



The remarkable conformation of the bones of the hinder part of the palatial region 

 in the Gangetic Dolphin has been well described by Eschricht, who pointed out that the 

 great lamella of bone which continues backwards the palatine portion of the maxillaries, 

 and passes outwards and upwards to articulate with the squamosals and frontals, is 

 really the pterygoid, and not the palatine as Cuvier supposed *. The easily separable 

 condition of the bones of the young Platanista skull in the Museum of the Koyal 

 CoUege of Surgeons has enabled me to confirm Eschricht's view ; for on removing this 

 plate the true palatine is seen, forming as usual the greater part of the anterior and 

 * Ossemens Possiles, 4"= edit. (1836) tome viii. p. 130. 



