120 
NATURE 
were deposited, lived a most temarkable group of herbi- 
vores, all of which were, roughly speaking, less specialised 
than any now on the face of the earth. The Oreodon, a 
ruminant about the size of a large domestic sheep, was 
there in considerable abundance, and must have lived in 
herds, after the manner of the bison in the neighbouring 
region. It was an animal of a strangely composite kind ; 
to the molar teeth of a ruminant it added the ulna and 
radius of a hog; it possessed a cranial and temporal 
region like that of the camel, and larmiers beneath the 
orbit as in the Cervida and the musk-sheep. Its canines 
were trilateral and worn like those of a pig, and its dental 
armature was complete all round. Three closely-allied 
forms, the Merychochcerus, Leptauchenia, and Agrio- 
cheerus, are associated with Oreodon, and form a group 
which, judged by existing forms of life, stands half-way 
between the pigs and the ruminants. It is an admirable 
instance of one of Prof. Huxley’s “ intercalary types.” 
The camel or lama was represented by two allied forms, 
the Poebrothere and Protomeryx, and the musk-deer by 
the Leptomeryx. The Artiodactyle division was present 
in very strong force. The Elotherium is allied to the hog, 
peccary, and hippopotamus. In a full complement of 
teeth it possessed a canine almost carnivorous in charac- 
ter. It was probably less omnivorous than any of the 
class now living. The Perchcerus, Leptochcerus, and Nano- 
hyus, form members of the same class, together with the 
Hyopotamus and the Titanothere, which was possessed of 
a well-developed and separate ulna and radius. The re- 
mains of rhinoceros indicate one, and perhaps two forms, 
during the American Miocenes. The lowness of the 
crowns of their teeth, the large d&velopment of the incisors, 
and the absence of any trace of horn-basis on the skulls 
which have been preserved, imply that they belong to 
the hornless section Aceratherium, of Dr, Kaup, rather 
than to the true rhinoceros. Dr. Leidy has very rightly 
separated Hyracodon from the true rhinoceros, because 
it has the full complement of teeth in both jaws. The 
Anchithere represented the horse in this fauna; the 
Palcolagus the hare; and there were also squirrels, 
beavers, mice, and hedgehogs present. 
There was also a corresponding development of the 
Carnivora. Two species of Amphicyon performed the 
function of the living foxes and wolves; the Hyzenodon 
that of the hyena; while the great Machairodus, and the 
allied form Dinictis, represented the lions, tigers, and 
other larger felines. 
If this fauna be compared with that of the European 
Miocenes, several important differences and resemblances 
may be remarked. The whole group of antelopes, found 
in such numbers in the classic plains of Pikermi by 
M. Gaudré, and in central France, are absent. The 
giraffe also, and the family of the Cervidee, and the horse, 
elephant, Mastodon and Hipparion of Europe, are equally 
absent. Other genera are common to both Europe and 
America. The £lotherium Moretoné of the Mauvaises 
Terres can scarcely be distinguished from the &, Aymardi 
of the Gironde. The Anchitherium Bairdi cannot be 
- distinguished with certainty from the 4. Aurelianense of 
France. The rhinoceros and Aceratherium of Eppelsheim 
and Pikermi find their analogues in the so-called 
Rhinoceros occidentalis and R. meridianus of America, 
while the Hyracodon recalls forcibly to mind the small 
[Fune 16, 1870 
rhinoceros from Sansan (Aceratherium Sansanense). 
The Lophiodon is also an American form. Of the 
Carnivores, the Amphicyon vetus is the equivalent of the 
A. major of De Blainville from Sansan, while the 
Hyzenodon and the sabre-toothed Machairodus were the 
scourge of the Miocene herbivores in America as in 
Europe. The family of the Oreodontidee, on the other 
hand, seem peculiar to America, as also the Titanothere 
and the small carnivore the Dinictis. 
This distribution of life throws considerable light on 
the physical geography of the northern hemisphere during 
the Miocene period. The absence of the South American 
forms which were living at the time, the apes, the rodents, 
and the edentata, implies the presence of a barrier between 
North and South America, which prevented migration 
from the one to the other ; and this barrier was most 
probably, as Prof. Huxley remarked in his last address te 
the Geological Society, an open sea, The forms of life 
common to Europe and North America imply a continuity 
of land between those now widely dissociated areas. Mr. 
Murray believes in the existence of a Miocene Atlantis, 
which has left the Sarghasso sea as a palpable monument 
of its existence in the mid-ocean, I should, however, be 
rather inclined to look for the continuity of land in the 
direction of Siberia, Behring’s Straits, and, it may be, 
Greenland ; and when the recent wonderful discoveries of 
temperate and sub-tropical vegetation in the now Arctic 
regions is taken into account, it appears to me extremely 
probable that the animals migrated from one area to the 
other by that pathway. But whether this be accepted or 
not, Prof. Heer has shown that during the Miocene times 
there was a vast extent of land, and a temperate climate 
in the now extremely high northern latitudes, which would 
imply conditions of life favourable for the migration of 
the Miocene animals. It is impossible to find out with 
any certainty the direction which the Miocene migration 
took, whether from America towards Europe and Asia, or 
vice versa. There is, however, one very significant fact 
to be observed, that the American Miocene fauna is less 
specialised than the European, or, in other words, that it 
is of an older type. It contains no true hyenas, nor 
deer, nor antelopes, nor any of the living genera which 
first appeared in the Miocenes of Europe. Possibly in 
point of time, or rather in homotaxy, it was older and 
more closely allied to the Eocene. The explanation which 
strongly suggests itself to my mind is that the migration 
set in from the old world, and that the above-named living 
genera sprang into being here, and are not found in the 
American Miocenes, because they had not time to reach 
that area. Thus the absence of certain extinct genera, 
such as mastodon and hipparion, may be accounted for. 
That eventually they found their way thither will be seen in 
the succeeding part of this essay relating to the Pliocene. 
W. Boyp DawKINS 
NAUMANN ON THERMO-CHEMISTRY 
Grundriss der Thermochemie. By §. Alex. Naumann. 
8vo. pp. viii. and 150; price 3s. (Brunswick, 1869. 
London ; Williams and Norgate.) 
T is not altogether without reason that modern chemists 
are accustomed to point,as a proof of their activity, to the 
amount of materials they have succeeded in accumulating, 
The fact, indeed, is sufficiently familiar to most students. 
