Fossil Organic Remains. £1 
order observed in the superposition of transition, secondary, ter- 
tiary, and alluvial formations, every where in harmony with the 
increasing analogy which the types of organization present ? Do 
these types succeed each other from below upwards, passing from 
the grey-wackes and black transition limestone, through the coal 
sandstone, Alpine limestone, Jura limestone, chalk, the tertiary 
gypsum, to the fresh water and modern alluvial formations, in the 
same order which we have adopted in our systems of natural his- 
tory, by arranging animals according as their structure becomes 
more complicated, and as 6ther systems of organs are added to 
those of nutrition ? Does the distribution of fossil organic bodies 
indicate a progressive development of vegetable and animal life 
upon the globe, — a successive appearance of acotyledonous and 
monocotyledonous plants, of zoophytes, Crustacea, mollusca ; 
(cephalopoda, acephala, gasteropoda), of fishes ; oviparous qua- 
drupeds ; of dicotyledonous plants ; of marine mammifera and of 
terrestrial mammifera ? Considering fossil organic bodies, not in 
their relation with such or such a rock in which they have been 
discovered, but simply with regard to their climacteric distribu- 
tion, is an appreciable difference to be observed between the spe- 
cies which predominate in the old and in the new continent, in the 
temperate climates, and under the torrid zone, in the northern 
and in the southern hemisphere ? Is there a certain number of 
tropical species which are found every where, and which seem 
to announce, that, independently of a distribution of climates 
similar to the present, they have experienced, in the first age of 
the world, the higu temperature which the cracked crust of the 
globe, strongly heated in its interior, had given to the ambient 
atmosphere ? Can the fresh- water shells be distinguished with 
certainty, by means of precise characters, from those of marine 
origin ? Is the determination of the genus sufficient for this 
purpose, or are there not (as among fishes) certain genera, the 
species of which live both in the sea and in rivers ? Although, 
in some of the tertiary rocks, the fluviatile shells occur mixed 
(for example, at the mouths of our rivers) with the pelagic 
shells, do we not observe, that the first form particular de- 
posits, characterizing formations, the examination of which has 
been hitherto neglected, and which are of very recent origin ? 
Have fresh-water shells ever been discovered under the Jura 
