XX INTRODUCTION. 
therium, Dichobune, Paleotherium, and Lophiodon, show- 
ing, with the fossils from the London clay, that the same 
peculiar generic forms of the class Mammalia prevailed 
during the eocene epoch in England as in France. 
Almost the sole exception to the generic distinction of 
the Eocene Mammalia which occurred in the researches 
of Cuvier, was the famous Didelphys of Montmartre: and 
what made this discovery the more remarkable was the 
fact that all the known existing species of that marsupial 
genus are now confined to America, and the greater part 
to the southern division of that continent. An Opossum 
appears to have been associated with the peccari-like 
Hyracotherium in the eocene sand of Suffolk ; where, like- 
wise, some teeth of a Monkey, apparently a Macacus, have 
been found. It is not uninteresting to remark that the 
Peceari, the nearest existing ally to the old Hyracothere, 
is, like the Opossum, now peculiar to America; and that 
two species of Tapir, the nearest living allies to the Lo- 
phiodon, exist in South America. We gain little, how- 
ever, from the comparison of the eocene with the exist- 
ing Mammalia, in reference to their geographical distri- 
bution, except a strong indication that the relative dis- 
tribution of land and sea, as well as the climate of En- 
glish latitudes, were then widely different from what they 
are at the present day. 
The marine deposits of the eocene epoch, in contrast 
with those of the preceding secondary periods, also be- 
speak the great advance of animal life, and show the re- 
mains of great Whales. Petrified cetaceous bones have 
been found in situ in the London clay at Harwich; and 
similarly petrified teeth and ear-bones, ‘ cetotolites,” have 
been washed out of the eocene clay into the Red-crag at 
So as > a al yo. pe = Re IP - ‘ . Bh 
Helixstow. These fossils, however, belong to species dis- 
