76—42 INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
S. titan ; and tlie resemblance of the different specimens to one another is so close 
that they may, at all events provisionally, be referred to a single species. That 
species is indeed a mnch smaller form than N. titan^ and many of its individuals do 
not greatly exceed in size the existing N. cristatus. The fossil species is distinguished 
from all living species of the genus (including Potamochcerus) by the extreme 
complexity of the structure of its cheek-dentition, as well as by the form of the 
skull. In the latter resj)ect it makes a very marked approach to S. harhatiis, but the 
simple molar dentition of that species removes it very widely from the fossil. The 
only way of explaining the resemblance existing between the crania of these two 
forms seems to be that they may both be diverging branches from a common stock 
having a cranium of similar form, and with molars of the simple structure of- the 
existing species. 
With regard to the fossil species in the list on pages 51-2 the present form is at 
once distinguished from S. antiquus, 8. erymanthius, and 8. major ^ by the structure of 
its molars ; those of the three fossil species being of the 8. titan type. 8. arvernensis 
is a much smaller form, with apparently simpler molars. The molars of 8. cJioeroides, 
8. cheer otheriim, 8. loclcharti, and 8 . qoalceochcerus, are all of a comparatively simple 
structure, and approach more or less closely those of 8. africanus and Ilyotherium ; 
while none of the other species in the list appear to present any close resemblance to 
the present form. The distinctness of the latter from the Siwalik 8. hysiidricus and 
Ilippohyus will be indicated in the sequel. 
Seeing, therefore, that the siDecimens under consideration cannot be identified 
with any named species with which the writer is acquainted, they are entitled to 
rank as a distinct species, for which the name of 8us falconeri is projDosed. There 
appears to be a certain amount of variation in the structure of the hinder molars, 
but not more than might be expected in different individuals of such a complex- 
toothed species. The high specialization of the species is indicated not only by the 
complex structure of the molars, but also by their extremely elongated form. 
Pesemhlance to Phacochoerns and Hippohyus . — Although there is no doubt that 8. 
falconeri is a true 8us^ yet in the structure of its molars it makes a decided approach 
to Phacoclmrus ; this character being most marked in last lower molars, like the one 
represented in plate VII., figs. 2, 9. This tooth approaches mTS of Phacochoerns in its 
extremely elongated form, in the flattened lateral walls of the main columns, in the 
distinctness and large size of the numerous accessory lateral columns filling the 
valleys, and in the relatively great height of the crown. To convert such a tooth 
into the lower molar of Phacochoerns, it merely requires that the main columns should 
be reduced to the size of the accessory ones, and that each one should be completely 
isolated from the others, while the height of the crown should be still more increased. 
The last lower molar of 8. falconeri is indeed almost exactly intermediate between 
the corresponding tooth of 8. titan and Phacochoerns ; and it is thus easy to see how 
a transition may have taken place from a simple tooth like that of 8. titan to the 
