Rev. A. Irving — On the Permian and Trias. 319 



both sj'stems are known. There is no instance of even a genus 

 common to both systems among the important classes Coelenterata, 

 Annuloida, Crustacea, Pisces, Amphibia, Reptilia, Mammalia ; and of 

 of the whole fauna it has yet to be shown that there is a single 

 species of any importance which ranges upwards from the Dyas into 

 the Trias, or conversely. 



General Conclusions. 



1. The general grounds on which geologists have been led to 

 draw a rough line of demarcation between the Paleeozoic and 

 Mesozoic Series have been so well stated by Sir C. Lyell in Student's 

 Elements, that it is needless to occupy space by repeating them here. 

 If, however, the terms ' Paleeozoic ' and ' Mesozoic ' are justified at all 

 (or the use of the more comprehensive term ' Cainozoic '), some 

 limit must be recognized in the application of them ; and on such a 

 principle of classification as is implied in the connotation of these 

 terms it is clear that the succession of life-forms must he admitted to 

 he of primary importance as evidence. On the other hand, evidence 

 obtained from the petrographical character or stratigraphical sequence 

 of the strata can be scarcely regarded as of more than secondary 

 value. The general impression left upon the mind is that, taken as 

 a whole, the series suggests on physical grounds the idea of a vast 

 period of transition from the more strictly Palgeozoic to the more 

 strictly Mesozoic condition of things, yet with a sufficiently definite 

 break in the succession of life-forms to warrant the division-line 

 being drawn where it has been, provided only the importance of it 

 be not exaggerated. The stratigraphical evidence in favour of 

 grouping them together is strong, so far as Germany and some areas 

 in Britain are concerned, but it is not supported by the lithological 

 character of the Alpine Trias; since in. the Alpine regions the 

 Permians are only very doubtfully represented by rocks now highly 

 metamorphosed, while the Triassic strata are almost entirely a 

 succession of marine deposits. The numerous organic remains 

 found in the latter strata, with their extraordinary admixture of 

 Palaeozoic and Mesozoic types, warn us however against attaching 

 too much importance to the facts presented to us in the English and 

 German areas which have so much in common ; at the same time 

 the jDalajontological facts connected with the Alpine Trias support 

 the view that the whole series is, on a broad and comprehensive 

 view, one of transition. If, on the other hand, we must have a 

 definite boundary-line, it is very difficult (and the difficulty increases 

 with the fuller investigation of the matter) to see how such a line 

 could be drawn otherwise than as it has been drawn, at the horizon 

 recognized in Germany as the boundary between the Byas and the 

 Trias. 



2. While a distinction is thus recognized, it would seem that it has 

 been by some geologists made too much of, and its importance 

 perhaps in some cases exaggerated ; and this has led to attempts to 

 make too much of the Permian system, to construct a forced and 

 artificial grouping for it in this country, by including within it 



