214 MIOCENE PERIOD. [Ch. XV. 



and concretionary limestone of a yellowish white colour : it is 

 finely exposed in the escarpments of Wildon, and in the hills 

 of Ehrenhausen, on the right bank of the Mur *. This coral- 

 line limestone is not less than 400 feet thick at Wildon, and 

 exceeds, therefore, some of the most considerable of our 

 secondary groups in England, as, for example, the Coral 



Ragf.' 



Beds of sandstone, sand, and shale, and calcareous marls, are 

 associated with the above-mentioned limestone. 



The third group, which occurs at a still greater distance 

 from the mountains, is composed of sandstone and marl, and of 

 beds of limestone, exhibiting here and there a perfectly oolitic 

 structure. In this system fossil shells are numerous. 



It is by no means clear that the coralline limestones of the 

 second group, are posterior in origin to all the beds of the first 

 division ; they may possibly have been formed at some distance 

 from land, while the head of the gulf was becoming filled up 

 with enormous deposits of gravel, sand, and mud, which may, 

 in that quarter, have rendered the waters too turbid for the 

 fullest development of testaceous and coralline animals. 



In regard to the age of the formations above described, we 

 may observe that the middle group, both in the basins of Styria 

 and Vienna, belongs indisputably to the Miocene period, for 

 the species of shells are the same as those of the Loire, Gironde, 

 and other contemporary basins before noticed. Whether the 

 lowest and uppermost systems are referrible to the same, or to 

 distinct tertiary epochs, is the only question. We cannot doubt 

 that the accumulation of so vast a succession of beds required 

 an immense lapse of ages, and we are prepared to find some 

 difference in the species characterizing the different members 

 of the series ; nevertheless, all may belong to different sub- 

 divisions of the Miocene period. Professor Sedgwick and Mr. 

 Murchison have suggested that the inferior, or first group, 

 which comprises the strata between the Alps and the coralline 



* Geol. Trans., Second Series, vol. iii. p. 335. f Jbid., p. 390. 



