D4 THE MEDALS OF CREATION. Cuap. II. 
agency of glaciers and icebergs. They are the catacombs of the 
extinct colossal mammalia—of the mastodon, mammoth, rhinoceros, 
hippopotamus, elk, horse, ox, whale, &c. They cannot be defini- 
tively separated from those of the Modern or Human epoch, for the 
gravel beds near Geneva, which closely resemble the newest tertiary 
drift in materials and position, abound in bones of animals, almost 
all of which belong to existing species.* 
Cerliary Eypochs. 
An extensive series, comprising many isolated groups of 
marine and lacustrine deposits, containing fossil remains of 
animals and vegetables of all classes ; the greater number of 
genera and species in the most ancient or lowermost beds 
belong to extinct types. 
Subdivisions :— 
1. The Priocenut (more new, or recent. Wond. p. 221); — 
strata in which the shells are for the most part of recent 
species, having only about ten per cent of extinct forms. 
(Norwich Crag.) 
2. The Miocenn (less recent, || Wond. p. 221) ; containing 
about 20 per cent of recent species of shells. (Suffolk Crag.) 
3. The Eocene (dawn of recent,§ in allusion to the first 
appearance of recent species—Wond. p. 226); the most 
ancient tertiary strata contain but very few existing species 
of shells; not more than five per cent. (London, Hants, 
and Paris basins.) 
* See M. Pictet’s “ Paleontologie.” 
t+ In the present state of our knowledge, this arrangement is of 
great utility, but it will probably require considerable modification, 
and must, perhaps, hereafter be abandoned ; for it cannot be doubted, 
that strata in which no recent species have yet been found, may yield 
them to more accurate and extended observations, and those in 
which only a few recent species are associated with a large number 
of extinct forms, may have these proportions reversed. 
{ From tAciwy, pletion, more; and kawds, kainos, recent. 
|| From pefwy, meion, less, and recent. 
§ From ds, eos, the dawn or commencement, and recent. 
