316 Notices respecting New Boohs. 



of England, Scandinavia, and Bohemia. Where such important 

 witnesses differ so materially in their interpretation of the facts, 

 those less versed in the stratigraphy of the Lower Palaeozoics can 

 scarcely hope to arrive at any very definite conclusion. Yet in 

 some places the unconformity would seem not to be restricted to 

 the same horizon. So much confusion arises out of the double 

 nomei_clatuie which now prevails that the issues are less clear 

 t'lan they might be. Nevertheless the base-line cannot be so 

 self-evident when a portion of the Llandovery rocks were at one 

 time classed with the Bala, and formed part of what is usually 

 known as Lower Silurian, but were subsequently separated from 

 the Bala series and transferred to the Upper Silurian. Moreover, 

 in the table at p. 22 we find that, whilst Sedgwick, Lyell, Hicks, 

 and Lap worth drew the line at the base of the Lower Mayhill, 

 Murchison, Jukes, Phillips, and the Geological Survey drew the 

 line at the base of the Upper Mayhill. Even granting that these 

 latter were altogether wrong, it is evident that the exact position 

 of this great break has not been so easy to determine in the 

 typical areas. 



When we come to the palaeontological evidence we are almost 

 aghast at the discrepancy between the calculations of Mr. Ethe- 

 ridge, as announced in his first Presidential Address, and Mr. Marr's 

 conclusions. " Analysis shows that, of the 613 Caradoc species, 

 103 pass to the Lower Llandovery (Upper Bala of Sedgwick) ; 

 but, strange as it may appear, 107 are common to the Caradoc and 

 Upper Llandovery, although we know of the stratigraphical break 

 which occurs between the two formations. This relation is chiefly 

 through the Actinozoa, Hydrozoa, and Brachiopoda, as we might 

 expect from their bathymetrical position and habitat " (Q. J. Gr. S. 

 vol. xxxvii. p. 134). Well may Mr. Marr enter a caveat against the 

 method of percentages ! Moreover, if these calculations are sound 

 they are equally fatal to Prof. Lapworth's " Ordovician" as a system 

 but this point must be left for specialists to decide. 



It is only proper to mention in this connection that Prof. F. 

 Schmidt, referring to the Baltic provinces of Russia, recognizes a 

 very marked distinction in the fauna of the Upper and Lower 

 Silurian, no intermediate group like the English Llandovery being 

 observed. " The -e is a clear break with us in the development of 

 organ : c life, notwithstanding the fact that the physical conditions 

 remain the same, for the Upper Silurian strata consist of Lim 

 stones and Marls, like those of the Lower Silurian" (Q. J. G. S. 

 vol. xxxviii. p. 525). Not with standing the distinction in their respec- 

 tive faunas, this physical resemblance yields additional testimony to 

 the systematic unity subsisting between the Silurian (Upper Silu- 

 rian) and Ordovician (Lower Silurian) ; and such is evidently Prof. 

 Schmidt's opinion, who regards the whole series of strata in the 

 Baltic provinces as one system, because all the strata are arranged 

 conformably, and the whole is covered unconformably by the Devo- 

 nian, the connecting lowest Devonian stages being altogether 

 unrepresented. Thus the stratigraphical conditions are, in some 



