158 PROCEEDINGS OF THE GEOLOGICAL SOcIETY. [Dec. l, 
means certain that such a difference really exists, since the means of 
comparison in the three cases are very different. 
Among the European species found in the palzeozoic rocks of the 
United States, the following species are found in Russia or the east 
of Europe, but are not known in this country :— 
Leptzna alternata, 
Spirifer biforatus, of the Lower Silurian series. 
var. lynx, chama, &c., 
Spirifer arenosus, 
aperturatus, 
Orthis eximia?, of the Devonian series. 
opercularis, 
Strophomena umbraculum, 
Fusulina cylindrica *, of the Carboniferous series. 
Should further examination discover a larger number of species 
under these circumstances, we might infer that at these remote 
periods the ocean was connected ead the whole of the northern 
part of the globe. 
The opposite table shows the proportion of species of different 
genera which are common to the United States and Europe in each 
of the three great divisions of the New York system, as shown in 
Mr. Lyell’s collections. 
Although the results of this table are liable to suspicion for the 
reasons mentioned at p. 157, they are worthy of some attention: it 
appears that while hardly a Gasteropode, and but few species of 
the Lamellibranchiate bivalves, are common to the older formations 
of Europe and the United States, above two-fifths of the Brachiopoda 
collected by Mr. Lyell are of European species. Most of the recent 
Brachiopoda are inhabitants of deep water; and the genera Lingula 
and Orbicula, which are fond of the coasts, give us no species common 
to the two continents: therefore the explanation of these facts may 
be that the inhabitants of deep seas have a wider geographical range 
than shells which are found near shore. Littoral species may re- 
quire for spreading themselves a continuous line of coast under a 
nearly equal climate, which are circumstances rarely likely to occur. 
But the inhabitants of the deeper waters being less subject to change 
of climate may be able to travel to greater distances. 
The comparison of the paleeozoic fossils of Europe and the United 
States does not bear out the opinion that those species which range 
through the greatest thickness of formations have also the widest 
geographical range; for we find im New York European species 
which are confined here to nearly a single bed as well as those which 
are common to several formations, and usually the species appear to 
have nearly the same vertical range in both countries. Thus :— 
Terebratula reticularis, Leptzna depressa, 
borealis, 
* De Vernenuil, Bull. de la Soc. Géol. de France, vol. iv. p. 12. 
