THEIR DISTRIBUTION. 
87 
entirely distinct from one another, and immediately suggest the second 
inquiry, to which we now proceed. What is the relation between the 
species of fossils, and the antiquity of their enveloping strata? That 
such a connexion between the age of a rock and its organic contents 
does certainly exist, and may plainly be recognised, will appear from a 
few facts which any one may verify by examining a good collection of 
Yorkshire fossils, or a sufficient suite of specimens from the same strata 
in other parts of England. The mountain limestone of the north-western 
dales of Yorkshire, abounds with crinoidea, product®, spiriferse, and 
bellerophontes, of which no single individual has ever been found in 
the strata of the eastern part of the county, which on the other hand, 
contain echini, trigonias, cucullasac, r os tel lari®, and ammonites, to which 
there is nothing similar in the west. The partition between these groups 
of strata and their fossils is made by the red sandstone stratum, which, 
in Yorkshire at least, has never yielded one single organic fossil. The 
same observation has been made in other parts of England. Again, in 
the eastern part of Yorkshire itself, a complete partition of the same 
kind is made by the blue clays of the vale of Pickering, between the 
chalk on the south and the oolitic rocks on the north ; both full of 
fossils, and those entirely different. 
I am sure that these assertions will not be disputed by any person 
at all acquainted with geological phenomena, or accustomed to distinguish 
the characters of fossils. The consequence flowing from them is of the 
highest importance and interest ; for, since it thus appears that a few 
shells brought from a quarry are data sufficient to determine the geolo- 
gical relations of the rock, we are entitled to conclude, that in a given 
district the age and position of certain strata, or groups of strata, are 
infallibly indicated by their organic contents. These researches, com- 
menced by Mr. Smith in England, have been extended with the same 
results over all parts of Europe, and a large portion of America, and 
therefore it is concluded that strata, or groups of strata, are to be dis- 
criminated in local regions, and identified in distant countries, by their 
imbedded organic remains. 
