102 MR. W. H. FLOWER ON THE OSTEOLOGY OF 
ascending branches of the caudal artery, so characteristic of a certain region of the tail- 
yertebree of the Cetacea, occur first in the fifth vertebra, but only on the left side; in the 
sixth they are seen on both sides, perforating the body of the bone, not the root of the 
transverse process. 
As in all Cetacea, the caudal vertebree suddenly change their characters at the point 
where they enter the laterally expanded part of the tail and where the chevron bones 
cease to be developed. ‘They now lose their cylindrical form, and become broad, de- 
pressed, and angular. There are seven such vertebre in the present specimen; and the 
eighth from the end of the series, or the eleventh caudal, reckoning from the be- 
ginning, is what may be called the transitional vertebra, being intermediate in form 
and size between its two exceedingly different neighbours. The last two show a 
rapid diminution in width. The terminal one is triangular in outline when seen from 
above. 
Nothing can well be more dissimilar than the lumbo-caudal region of the spinal 
column in Jnia and Platanista. In the latter the short bodies, the long narrow trans- 
verse processes, and high spines curving forwards and bearing immense laterally deve- 
loped oblique processes with (throughout the lumbar region) well-marked anterior and 
posterior articular surfaces, form most striking distinguishing characters. 
The chevron bones sent with the skeleton are ten in number. It is probable that 
the first is wanting, as there is none corresponding with the form this usually has in 
the Cetacea. I have therefore indicated its situation with a dotted outline in the figure 
of the vertebral column (Pl. XXV. fig. 2). These bones agree in general characters 
with the processes of the vertebra with which they are connected, being of moderate 
length, very broad and rounded at their free extremity. The lateral halves of the last 
three are not united in the middle line. 
There are thirteen pairs of ribs (Pl. XXVII. fig. 2), the last being well developed 
and articulating with the transverse processes of the corresponding vertebrae. ‘They 
are stout and heavy for their length, more so than in the ordinary Dolphins. In their 
comparatively cylindrical form they present a marked contrast to the broad flat ribs of 
Platanista. The last two or three are, however, much more compressed than the 
others. The curve, very strong and angular in the first, gradually diminishes and 
becomes more regular. ‘The last has a slight turn outwards at the lower end, giving a 
gentle sigmoid curve to the whole bone. 
The anterior ribs have long and broad, somewhat compressed capitular processes, 
with distinct articular surfaces at the extremity and at the tubercle. In the fifth the 
length of this process is sensibly diminished. In the sixth, seventh, and eighth it 
shortens rapidly, the two articular surfaces being already confluent in the seventh. In 
the ninth a rounded projection of the lower border of the vertebral end indicates the 
rudimentary process; in the tenth it has diSappeared altogether, and henceforward the 
upper end of the rib ends in a somewhat dilated, oval, convex, articular surface, gradu- 
