ANNIVERSARY ADDRESS OF THE PRESIDENT. 165 



Leptcena depressa and Leptcena euglypha^ are precisely those shells 

 which have a great vertical and horizontal range in Europe — species 

 which were capable of surviving many successive changes in the 

 earth's surface, and for the same reason enjoyed, at certain periods, 

 a wide geographical range. It has been usually affirmed that in the 

 rocks older than the carboniferous, the fossil fauna in different parts of 

 the globe was almost everywhere the same ; but Mr. Lyell adds, " that 

 however close the general analogy of forms may be, there is evi- 

 dence in the Silurian rocks of North America of the same law of va- 

 riation in space as now prevails in the living creation : " and in 

 another place he states, that with regard to the proportion of species 

 common to the Silurian beds of Europe and America, whether of 

 the upper or lower division, he can confidently affirm that it is not 

 greater than a naturalist would have anticipated, from the analogy 

 of the laws governing the distribution of living invertebrate animals. 

 While the remains of fucoid plants are met with abundantly 

 in the Silurian rocks of Europe and in the lowest members of the 

 series, I am not aware that any vestiges of land plants have yet 

 been discovered in them. Sir R. Murchison says, that in the older 

 palaeozoic rocks of Russia he met with no signs of terrestrial fossil 

 vegetables. Fucoids are plentifully distributed through every part 

 of the series in North America; and Mr. Lyell also states, that in 

 the Hamilton group, which corresponds in many of its fossils with 

 the Ludlow rocks, and which, singularly enough, is met with in the 

 neighbourhood of Ludlowville, remains of plants allied to Lepidoden- 

 dron have been found associated with fossils agreeing perfectly with 

 European Upper Silurian types ; and that other plants allied to 

 these, and ferns, have been met with in the lowest Devonian strata 

 of New York, associated with fossil shells closely allied to the Silu- 

 rian. Thus we have additional proof, if any were wanting, of the 

 existence oi' dry land at the time of the deposition of these Silurian 

 beds. 



Devonian Rocks. 



The Silurian rocks of Russia in Europe are covered conformably 

 by deposits, the identity of which with the Devonian or Old Red 

 Sandstone series of the British Isles, Sir R. Murchison and his compa- 

 nions clearly made out. They extend over an area of not less than 

 150,000 square miles, a superficies greater by nearly one-third than 

 that of Great Britain and Ireland together. This monotony of fea- 

 ture over so vast a space is even greatly surpassed by the Permian 

 rocks ; and when it is considered that this uniformity is combined 

 with a stratification rarely deviating from the horizontal, never 

 thrown up into natural sections, and that the investigation of them 

 can only be carried on where the beds are exposed in the banks of 

 rivers, geologists can appreciate the tedium and labour of exploring 

 such a country, and cannot too highly praise the patience and per- 

 severance of Sir R. Murchison and his fellow-travallers. 



Although recognized by a remarkable degree of identity in fos- 

 sil contents, and especially in regard to ichthyolites, as a deposit 



