xxx FACTS AND OBSERVATIONS. 



Every one of these affiliated areas (and many more will in future be added to them) is con- 

 nected with Bohemia by different groups of extinct life, different in the connecting genera and 

 species both in kind and proportions these peculiarities being regulated by local circumstances. 



England, Wales, and Ireland are remarkable for the great number of their Brachiopoda and 

 Cephalopoda identical with species in Bohemia. 



If from these western frontiers of Europe we cross the Atlantic, we shall find in North-east 

 America forty-three species of Mollusca identical with those of Bohemia, a very suggestive fact, 

 on which the space allotted here will not allow me to speak. 



In Great Britain, France, and Spain the Bohemian species are much the same, but each 

 country has a few peculiar to itself. Scotland has Calymene brevicapitata, Rhynchonella cuneata, &c. 

 Wales has Chonetes minima, Leptaena aquila, Orthis lineata, a Calymene, an Agnostis and a Remo- 

 pleurides. France has Graptolites testis, Orthis redux, Rhynchonella Ceres, a Homalonotus, a 

 Bronteus, &c. In every region the nature of the fauna depends on the fact of deposition or non- 

 deposition of certain beds, and on the effects of denudation. 



M. Deshayes shows very forcibly how close are the vital relations of these portions of the Silu- 

 rian deposit of Europe, by asserting that any two basins have intim*ate relationship when they each 

 possess twenty identical species, for a still larger identity of genera is sure to follow. But there are 

 areas coeval, or nearly so, which have scarcely a species in common, because peopled under different 

 conditions such as Canada East (Quebec) and Western Newfoundland, such as the eastern and 

 western ends of the Clinton group (New York) . The connexion of the Prague basin with others 

 appears to be much closer than could have been expected, looking at distances and the ever active 

 influence of locality. 



The Bohemian species in England and Wales must be considered a very large number. The 

 Table P shows their distribution. Hitherto Scotland has not yielded its full tribute of life ; it 

 therefore exhibits a less prominent amount of unity with Bohemia. 



The similarity of the Silurian life of France, Spain, Portugal, and Sardinia to that of Bohemia 

 is very striking, and it is rendered the more so by the imperfect manner in which these countries 

 have been searched. France came under the careful survey of very eminent men at atime when 

 organic remains were little regarded. Since that period MM. De Verneuil, Rouault, Triger, 

 Caillaud, and Bureau have made considerable collections, not wholly published. 



At the time when the Silurian mollusks of Spain and France were deposited the Pyrenees did 

 not exist, and one great Silurian ocean, filling those two broad regions, occupied much of the interval 

 between these western frontiers of Europe and Bohemia, stretching with many a devious shore of 

 Laurentian and other rocks far into the east and north. 



Table N shows that the most remarkable points in the fauna of Spain and France are the 

 abundance of Trilobites in species identical with those of Bohemia, the paucity of identical Bra- 

 chiopoda and Cephalopoda, and the absence of Gasteropoda. 



Two species of Spanish Trilobites met with in Bohemia are Primordial (an Arionellus and a 

 Conocoryphe) ; and eleven or twelve of them are of the Caradoc age, the equivalent, more or less 

 exactly, of the Bohemian stag% D. But in France no Primordial Trilobites are known; while 

 thirteen of its species are in the stage D, just mentioned, and two, Bronteus Thysanopeltis, Cyphaspis 

 Burmeisteri, are Upper- Silurian in Bohemia and France. The places of first appearance of these 

 species are therefore mostly doubtful at present. 



These two great regions are apparently poor in the other Silurian orders. Spain at present 

 only yields twenty-five Bohemian species, but France, having been better worked, gives forty-eight 

 numbers, however, which are merely temporary. 



Russia maintains her connexion with Bohemia only by a few Brachiopoda, one Trilobite, 

 six Coelenterata, and six Cephalopoda, and this not for want of research ; for a celebrated visit of 

 three distinguished geologists made palaeontology fashionable in Russia. Baltic Russia is nearly 

 as poor in Bohemian life. 



