16 CORRELATION OF GEOLOGICAL FAUNAS. [bull. 210. 
What is actually meant in such classification is that the individual 
specimen to which a particular specific name is applied exhibits in its 
morphological structure the characters which have been described 
under the specific name used. In the same way, to say that a certain 
animal or plant belongs to a particular genus means that it possesses 
the characters to which the generic name used has been scientifically 
applied. 
The specific and generic name given to a fossil applies to the peculiar 
morphological characters recognized in the scientific definition of the 
species or genus, and in giving it we are not dealing with the individ- 
ual as a whole or with aggregates of individuals, but only with the 
particular characters exhibited by the individuals implied by the 
name. When, for instance, it is stated that Phacops bufo lived as 
long as a third of the time represented by the Devonian system, it is 
not meant that any individual specimen continued to live so long, but 
that in genetic succession the specific characters of the species Phacops 
bufo were repeated without noticeable and permanent modifications 
during that period of time. We are not dealing with the biological 
aggregate, a taxonomic species, but with the geological aggregate, a 
living succession of individuals — the race. 
The terms of zoological and botanical classification are constructed, 
primarily, to apply to living organisms — animals and plants. A fauna 
has thus come to mean, in scientific usage, an aggregate of animals 
of different kinds structurally, associated on the basis of somo condi- 
tions existing outside the animals themselves. These conditions may 
be kind of element, as air, water, or land inhabited; place, as coun- 
try, mountain, sea; altitude, as plain, plateau, or mountain, or zones 
of depth in water, or geological formation, or kind of sediments in 
which the remains are preserved as fossils. Flora is a term for the 
aggregate of plants under like conditions. 
DISTRIBUTION AND RANGE. 
When the conditions determining the classification of the fauna or 
flora are geographical, the boundaries and their measurement are 
spoken of as geographical distribution. Thus the fauna is said to be 
distributed over a country or through a number of degrees of latitude^ 
or through a number of feet in altitude above the sea, or through a 
number of fathoms of depth below sea surface. Geographical distri- 
bution is concerned with the relation of organisms in faunal or floral 
aggregates to the position of their living, if living forms, or of their 
burial if fossils. 
Range and geological range are terms which signif y that the criterion 
of association is geological rather than geographical, and refer to the 
association of organisms with geological formations. Thus a genus is 
said to range from the Cambrian to the Devonian systems; or the 
geological range of a species or fauna may be said to extend from one 
