2

PALAEONTOLOGY.

forms, and establishes the great fact, that whole races of animals and vegetables havelived and passed away: nay, it does more than this,—it proves that at successiveepochs the assemblages of organic beings have been totally different in their specificcharacters from those now living, though in no instance created on principles of lifedifferent from those developed in existing organisms.

Some of the results which may be derived from this fact are ably set forth in theTables of Bronn’s ‘ Index Palseontologicus,' made known to English readers byProfessor John Nicholl, and which will be now quoted, being preceded by the smallexplanatory Table of Formations which he has prefixed.

a. Lower Silurian.

b. Upper Silurian .

c. Devonian .

i. CarboniferousPeriod.

J d. Mountain Limestone.

e. Coal Formation.

f. Lower New Red Sandstone.

g. Zechstein .

b. St. Cassian Beds.i. Variegated Sandstone.

k. Muschelkalk.

l. Keuper .

n. Trias Period. J

' m. Lias.

n. Oolite.

o. Kimmeridge Clay.

p. Wealden.

hi. Oolite Period.

~ Neocomien.Greensand.Chalk.

iv. CretaceousPeriod.

' s. Nummulite Formation.t. Calcaire grassier,v. Tertiary Pe- _ Middle Tertiary,riod. »• Molasse.

w. Upper Tertiary.I x. Diluvial.

y. All fossil species together.

z. Living.

i. —v.

The object in referring to the Tables being in this Essay a practical one, many ofthe speculative reasonings which might be founded upon them will not be broughtforward in a detailed manner. It is right, however, to allude to some of them beforesubmitting the Tables for consideration. The duration of species is a subject of greatinterest, whether viewed as a geological or as a zoological question. It is knownto us as a fact dependent on a great Law of Nature , that each individual has anaverage duration of existence, varying in extent with different species; but it has been