INIA GEOFFRENSIS AND PONTOPORIA BLAINVILLII. 89 
As Inia has always been supposed to have certain affinities with Platanista, 1 
have in the following description compared the different bones with those of that sin- 
gularly modified Cetacean on the one hand, and of several of the ordinary Delphinide 
on the other. Fortunately the Museum of the College of Surgeons contains a 
skeleton of the Gangetic Dolphin of nearly corresponding age with the subject of 
the present communication, and I have also had frequently to refer to Eschricht’s 
valuable memoir upon the species *, 
The leading features of the skull have already been made known by d’Orbigny and 
Gervais ; but I am able to add some further details regarding its structure, 
A comparison of the two skulls at the British Museum sent by Mr. Bates, with the 
present example, shows only such differences as might be expected from the greater 
age of the former, such as a more marked development of the ridges and prominences 
in proportion to the size of the brain-case. The postnarial prominence especially is 
more elevated and angular in the older specimens. The teeth differ somewhat in 
number, as will be mentioned further on. 
The principal dimensions of the three skulls are as follows :— 
Collected by 
Mr, Bates, npn Mr. Bartlett. 
a, . 
a eee ss ST |e] ey eT 
EximeMeslensuieeen aver ete rc. echoes eet rae hee 20°77!" 19-4" 16-7" 
Length of rostrum (from anterior end of premaxillary to bottom 
of antorbital notch of maxillary)....... ............ wala) Low 12°7 11:0 
From anterior end of premaxillary to lower edge of nasal bones .|_ 16-7 15-7 136 
From anterior end of premaxillary to hinder edge of palate 15°7 t 126 
Greatest breadth, across zygomatic processes of squamosals 9-4 8-1 7:0 
Breadth of foramen magnum..........e.00--.0 seceeeee ee. 1-4 1-2 1:3 
Breadth of the occipital condyles .......... 00 ..ce sc cses cess 3:2 3:0 2:9 
Breadth across antorbital processes of frontals................ 6-1 5:3 45 
Breadth of rostrum at base (bottom of antorbital notches off 
Rip tl haut) MAGE Domai Sere POONER, meee ee mee ee eee 4:2 3:5 3:1 
Breadth of rostrum at middle ............. tépepmoengaee 5 14 12 aE 
Miemidible lengthy psjists oes Sep Bhs tarts eae sete sce. Seed ot 18-2 17-0 14-2 
HSM OUR OL MYM PLVAIG ls ctor ns) 4 dics nieve, seach tee 9:8 9-4 73 
Greatest breadth across the posterior ends of the rami..,... .... 8°7 73 65 
Height of ramus at coronoid process... ......0..0eec. ee veee 3-9 3:4 29 | 
The want of symmetry so prevalent in the skulls of Dolphins is but slightly marked. 
It can, however, be detected in a slight twist to the right of the hinder part of the 
narrow median space between the premaxillary bones, and in the greater elevation on 
the same side of the postnarial prominence of the frontal bones, Both maxillary and 
premaxillary bones extend backwards to an equal extent on the two sides, 
In the cranium of the young specimen which forms the subject of the present commu- 
* “Om Gangesdelphinen,” Trans, Roy. Dan, Acad, 1851, Translated in Ann, & Mag. Nat. Hist. for March 
1852, + Broken, 
02 
