108 MR. W. H. FLOWER ON THE OSTEOLOGY OF 
below. The alisphenoid is concealed by a plate of the pterygoid, which articulates with 
all three bones just mentioned. 
The orbit is slightly larger in proportion to the length of the cranium than in Jnia, 
and therefore considerably more so than in Platanista. The upper margin forms a 
wider arch than in the former; the postorbital process is broader and shorter; the 
antorbital tuberosity much smaller, but still chiefly formed by the malar bone. The 
styliform processes are unfortunately broken off. 
The upper surface of the skull is remarkably flat, showing scarcely a trace of the 
postnarial elevation. On this surface the frontal bones appear in a narrow, slightly 
raised median piece behind the nasal bones, ‘7” long, and ‘5 wide, bounded laterally 
by the posterior extensions of the maxillaries—and on each side in the supraorbital 
plates, of which a much broader piece is left uncovered by the maxillaries than in 
Inia. The nasals are flattened, irregularly quadrate plates, as in Inia, but, in con- 
sequence of the direction of the frontals, lying nearly horizontally instead of vertically. 
The narial aperture is broader, but shorter, than in Jnia, being encroached upon by 
the largely developed antenarial tuberosities of the premaxillaries, which are broader and 
flatter on the surface than in Inia. The upper obtusely pointed ends of the pre- 
maxillaries extend to a level with the inferior border of the nasals, but do not arti- 
culate with them, as a strip of the maxillary comes between. The hinder ends of 
the maxillaries are broader and flatter than in Znia; but in front of the nostrils they 
are much more contracted, and above the orbits have.a small but distinct. longitudinal 
crest, *3" high at the middle and gradually subsiding at the ends. This is not a mere 
elevation of the edge of the bone, as in Jnia, but a distinct ridge placed some way within 
the suture between the maxillary and the orbital plate of the frontal, and of which there 
isno trace in /nia. Between this crest and the elevated portion of the premaxillary there 
is a very deep and narrow fossa, continuous in front with an extremely narrow but deep 
groove, which lies between the maxillary and premaxillary along the entire length of the 
rostrum, and which is only faintly indicated in Jnia. The rostrum is considerably 
longer and narrower in proportion to the size of the cranium than in Jnia. 
The palate-bones resemble those of Jnia in not covering the vomer in the middle 
line. They have a small free external plate. Unfortunately the greater part of the 
pterygoids is broken away; but enough remains to show that these bones do not conform 
to the type of the ordinary Dolphins, but are arranged in a peculiar manner, apparently 
intermediate between those of Inia and Platanista. A broad outer lamella, resembling 
that so characteristic of Platanista, remains on each side, and, though not covering the 
palatine anteriorly as in that genus, passes upwards and outwards to the temporal 
fossa, overlying the alisphenoid and articulating with the squamosal, parietal, and 
frontal 
The petrotympanic bones are wanting on both sides, showing that their mode of 
attachment resembles that of nia rather than that of Platanista. 
