10
THE ESSEX NATURALIST.
partially domesticated by Palaeolithic man himself, as suggested
by occasional marks which look like halters in his drawings ;
but, as Prof. Duerst24 well observes, "no one is able to determine
with certainty, from the study of a few bones of a fossil
or a sub-fossil horse, whether the individual was wild or
domesticated."
Rhinoceros.—There seem to have been three species of
rhinoceros in western Europe during the Pleistocene period,
but they are not easily distinguished by fragments, and only
one, the woolly rhinoceros (R. antiquitatis) which always occurs
with the mammoth, has readily recognisable upper molar teeth.
The latter species seems to be closely related to the great white
rhinoceros (R. simus) which still survives in Africa. With it
sometimes occurs the slender-nosed rhinoceros (R. mercki of
continental authors, R. leptorhinus of Owen), which is best known
by the fine skull and mandible found by Sir Antonio Brady at
Ilford. This species, however, occurs more usually with
hippopotamus, and both it and a stouter early form (R.
megarhinus) are found at Clacton. The megarhine rhinoceros
is also represented by fine jaws from Grays.
Elephas.—It seems at first easy to distinguish and classify
the different molar teeth of Pleistocene elephants. The Pliocene
fossils show that the constituent plates of an elephant's molar
are really transverse ridges which have gradually become
deepened and compressed. Hence, the deeper the ridges and
the greater their compression, the later the geological age to which
the tooth should belong. Only in a general way, however, is
this inference well founded. It is true that in the latest Pliocene
deposits, and even in the Norfolk Forest Bed, there is a low-
crowned, wide-plated form of molar (E. meridionalis) which never
occurs later. It seems to give rise to a slightly deeper and more
laterally-compressed form of molar (E. antiquus) which is partly
contemporaneous but chiefly occurs later and is found specially
with the Pleistocene hippopotamus. It also passes into a broad
form of molar with thinner or more compressed plates, which is
again partly contemporaneous (E. trogontherii), but is succeeded
eventually by an excessively deepened molar with specially thin
24 J. V. Duerst, in R. Pumpelly, Explorations in Turkestan (Carnegie Inst., Washington,
pub. no. 73, 1908), p. 385.