398 REV. A. IRVING ON THE DYAS (PERMIAN) 
a general broad physical distinction between the two groups of 
strata as they are developed in Central Europe. 
This character applies also to some extent to the Zechstein. The 
Upper Rothliegende, it must be borne in mind, is never overlain by 
the lower and middle members of the Zechstein, though it is by the 
Plattendolomit, or uppermost member of that formation. Then 
again the horizontal variation of the strata of the Zechstein series 1s 
very marked and noteworthy. At one place the lower and middle 
members of this series consist of marls abounding in gypsum, which 
is extensively worked in many localities; at another, the Lower Roth- 
liegende is succeeded in ascending order by the normal sequence of 
Kupferschiefer, Middle and Upper Zechstein strata ; in others again 
the normal Kupferschiefer and Middle Zechstein are replaced by 
the conglomerates known as ‘‘ Grauliegende,” with an ashy grey- 
green matrix, derived for the most part from the tufts associated 
with the quartz-porphyries and felsites of the adjacent primeval 
land. The importance of these facts can perhaps be only fully 
appreciated in the field; yet when one contrasts this horizontal 
irregularity of the upper members of the Dyas group with the uni- 
form character of each of the three members of the overlying Trias, 
as they are exposed over hundreds of square miles in Middle and 
Southern Germany, and the regular and conformable succession 
of the Bunter, Muschelkalk, and Keuper, we find a striking contrast 
between the German Dyas and Trias, based on physical facts 
alone, the importance of which, when taken along with the pale- 
ontological evidence, can scarcely be denied or explained away. 
GENERAL RELATION OF THE PERMIAN TO THE TRIAS. 
Since Murchison wrote on the Permian Group the extension of 
our knowledge of this group and of the Triassic Group of strata has 
placed us in a position to form a more correct perception of their 
relation to one another in the European series of rocks; and this 
has mainly come about, thanks to the labours of our German and 
Austrian confréres, by the more accurate knowledge which we now 
possess of the marine conditions of the Triassic period, as they are 
recorded in the many thousands of feet of strata of Triassic age 
which cover extensive areas on both the northern and the southern 
sides of the Eastern Alps. I have attempted elsewhere* to give a 
succinct account of those strata, and need not therefore occupy space 
here with any details. Special reference, however, may be made to 
the writings of Credner, Von Hauer, and Giimbel, and to the splendid 
monograph of Mojsisovics on the Alpine Cephalopoda. 
Taking a broad and general view, we may say of the Permian 
and Trias that they are inversely proportional: the former, so 
far as the HEuropean area is concerned, is essentially a northerly 
system, thinning out towards the south (a fact which Murchison 
recognized); the Trias, on the other hand, is essentially a southerly 
system, becoming more and more feeble in its development towards 
the north. 
* Vide Geol, Mag. Nov. 1882, p. 494. 
