4 
MOLAR TEETH AND OTHER REMAINS OE MAMMALIA. 
In endeavouring to refer to their respective species a large series of molar teeth 
of Rhinoceros now in the collection of the Indian Museum, I found the great want 
of good figures and descriptions of the known fossil species with which new ones 
might be compared. In the present memoir I have endeavoured to remedy this 
want by giving figures and descriptions of the molar teeth of these old species, 
together with those of others which could not he referred to any of them. 
Eor the technical names assigned to the different portions of the molar teeth of 
Rhinoceros^ I may refer to Mr. Boyd Dawkins’ paper on the molars of Rhinoceros 
tichorhinus (Nat. Hist. Rev., 2nd Ser., Vol. 3, p. 526), where they will be found 
fully explained. There is also a list of most of these terms given in Mr. Eoote’s 
Memoir in the first part of this volume. 
In the old Siwalik area it will be found that, including the new species here 
described and the Perim Island species which has lately been discovered in the 
Siwaliks by Mr. Theobald, there were five species inhabiting the Sub-Himalayan area, 
though not perhaps all living in the same spot. The assemblage of such a large 
number of forms of the same genus in a limited area is, to say the least, very 
remarkable, and one is led to wonder how or for what purpose so many distinct 
species were differentiated at the same time. The explanation is probably to be 
found in the existence of an abundant supply of food suitable for the nourishment 
of large herbivores, and in the presence of a large area for them to wander over. 
Herbivores, such as the Elephants and Rhinoceros of the Siwaliks, were of too 
large a size to he much molested by the attacks of Carnwora^ and they were also, 
as far as we know, free from human persecution. Under such circumstances the 
species of a genus might increase almost indefinitely in number. It appears to 
me probable that when in any given area the conditions of life are peculiarly 
suitable for a genus of animals, in that area one would expect to find a great 
number of species of that genus ; the production of species being, according to my 
ideas, merely an extension of the production of individuals. In a suitable area, the 
number of individuals would clearly be large, and some of them would vary, and 
so would originate a new species. When the physical conditions in the same area 
became less favourable to the genus, the “ survival of the fittest ” would come into 
play, and the less hardy or less modifiable forms would die out. In the gravels of 
the Thames valley three species of Rhinoceros lived contemporaneously in the same 
area,* being, I think, next to those of the Siwaliks, the largest number of species 
in one area. 
Rhinoceros Pal^indictjs, Falconer. PI. 4, figs. 3 and 4. 
Of the upper molar teeth of this species of Siwalik Rhinoceros, we have no 
very complete specimens in the collection of the Indian Museum ; I have therefore 
been obliged to content myself with figuring the imperfect but characteristic 
( 22 ) 
* Boyd Dawkins : Nat. Hist. Rev., 1865, p. 403. 
