370 THE MEDALS OF CREATION. Cuap. X. 
GENERA, SPECIES, 
Carboniferous System . . 1 1 
Purassic 4: + 6g ke Lae 20 
Cretaceous » 6 3 4 4 «/@4 280 
Pertiaty 0 stds Vee 460 
Living in the present Seas . 68 1000 
Of the recent species, 575 inhabit the Tropics. 
390 Temperate zones, 
—- 75  —— Cold regions. 
The above statistical view was published six years ago ; 
but the great activity of research that has since prevailed, 
has largely augmented the known number both of fossil and 
recent forms. M. D’Orbigny’s recent Tables* give for the 
Jurassic or Oolite 10 genera ; Cretaceous, 38 genera ; Ter- 
tiary, 60 genera ; but this estimate must be far too low. 
I have thus endeavoured to convey a general idea of the 
highly important results obtained by the microscopical 
investigation of the minute organisms that enter so largely 
into the composition of many of the fossiliferous deposits. 
Without the aid of the most perfect optical instru- 
ments which modern science and art have produced, even — 
the existence of many of these structures could not have — 
been demonstrated ; and we cannot doubt, that were the — 
powers of the microscope increased, the fossil remains of 
beings still more minute would be detected ; and that rocks 
and strata which now appear to consist of amorphous par- 
ticles of lime, of silex, and of iron, would prove to be the 
ageregated skeletons of animals, yet more infinitesimal than — 
those which have formed the subject of our contemplations. 
How strikingly illustrative are these phenomena of the pro- 
* Cours Elémentaire de Paléontologie. 
= teeta 
