REPORT ON GEOLOGY. 
399 
of rocks; but these have been now elevated to the rank of a 
venerable antiquity as compared with the more recent tertiaries 
of the Loire, and still younger deposits of the Sub-Apennines 
and Sicily. These distinctions will be found as well marked 
as any between the secondary formations; and still more im¬ 
portant in the inferences to which they lead. The researches 
of Desnoyers, Prevost, and Marcel de Serres appear to have 
led the way in these investigations; but Des Hayes, Basterot, 
Tournal, Reboul, and the Venetian Catullo, have ably coope¬ 
rated ; our own countrymen also, especially Murchison and 
Lyell, have brought to this subject all their usual zeal and in¬ 
telligence : the former has materially contributed to the eluci¬ 
dation of the tertiary formations of the Alps and Germany ; 
and the latter has, in conjunction with Deshayes, produced 
complete lists of the fossil shells of the several successive 
tertiary formations, designating in each the proportion which 
the fossil species apparently identical with those still existing, 
bear to these which appear to be extinct *. 
* It has been ascertained that the inferior, middle and superior group of ter¬ 
tiaries contain respectively the increasing proportions of 3, 19, and 52 per cent, 
identical with actually existing species among their fossil shells. It is interest¬ 
ing also to observe that while the inferior group passes insensibly into the sub¬ 
jacent secondaries by a kind of transition beds at Gosau and Maestricht, the 
superior group in its upper limits equally approximates to the actual order of 
things, some of the highest beds at Nice and in Sicily (although here elevated 
many thousand feet above the present level of the sea,) containing of 
recent species. May not the sands with recent shells observed at a height of 
1000 feet by Mr. Trimmer in Snowdonia, and those mentioned by Mr. Gil¬ 
bertson in Mr. Murchison’s Report to the former Meeting of this Society at 
York as occurring, though at a less elevation, in the inland parts of Lancashire, 
belong to the same mra? 
The mammiferous remains imbedded in these groups observe a similar pro¬ 
gression, extinct palseotheria, &c., alone occurring in the lowest group, while 
the middle group exhibits these with the mixture of the elephants, &c., of our 
own diluvial gravel, and the latter class become prevalent in the superior group 
to which our own crag is referred. 
It is further important, as displaying the great variety in the mineral consti¬ 
tution of rock formations of the same sera, and evincing how impossible it is to 
take that character as any criterion of their geological age, to observe that the 
single group of tertiaries (that occupying the middle place) contains, near Aix, 
rocks which, without an examination of their geological position and organic 
remains, might have been confounded with those of our own coal measures : and 
again in the nagelflue and molasse of Switzerland, &c., conglomerates and sand¬ 
stones like those of the pcecilitic group ; similar rocks at Cordona in Spain, and 
probably also in Poland, containing salt and gypsum, which constitute a further 
resemblance; and lastly, in Lower Styria, coralline limestone like our own mid¬ 
dle oolites alternates with this series. 
M. Boue has recently suggested that much of the tertiary districts of Bel¬ 
gium, North Germany, and Poland appear to him to belong, not to the inferior 
or Parisian group, but to the superior or Sub-Apennine systems. 
