Geological Society. 293 



of the Palaeotherian period, and ascending through the middle Sub- 

 Apennine system to a large group of strata, apparently containing 

 several species of recent shells, and of the same age with the higher 

 deposits of the Vienna basin. Yet in this most recent group are masses 

 of limestone exhibiting so fine an oolitic structure, that by hand spe- 

 cimens alone we should find it no easy task to separate them from the 

 great oolite of Bath. 



In another section from north to south, we have shown the asso- 

 ciation of the upper tertiary groups with the rugged volcanic rocks 

 which start out from the eastern plains of Styria : and from all the 

 complicated phenomena we conclude, that the volcanic forces were 

 first called into action in this region during the most recent tertiary 

 period, and were probably continued for a long succession of ages, 

 during which the sea was spread over the lower portions of Styria 

 and Hungary j and that no test can be established whereby we can 

 fix the ages of the different igneous productions : inasmuch as the 

 same groups of strata are in one place covered by basaltic lava, in 

 another by trachyte, in a third by volcanic conglomerate, and in a 

 fourth alternate with volcanic sand and breccia. Lastly, we have in 

 the discontinuous masses of volcanic breccia, and in the rude and 

 interrupted escarpments of trachytic and basaltic rocks, the clearest 

 and most emphatic proofs of enormous degradation, within a period 

 of time bounded by one of the newest regular formations of geology. 



Before quitting this subject, I may add that Mr. Murchison has, in 

 his last Memoir, identified all the groups of the Vienna basin with 

 those of our Styrian sections. The inferior blue marl (or Tegel) of 

 that basin is supposed to be the equivalent of the London clay j the 

 white coralline limestone of the Leitha-gebirge is placed on the same 

 parallel with the limestone of Wildon j and the higher accumulations 

 of sand and gravel are compared with the upper formations of Lower 

 Styria, through which, as stated above, the basaltic and trachytic 

 eruptions have made their way. 



The papers of Colonel Silvertop, on two lacustrine deposits in the 

 province of Granada, placed before us an interesting sketch of the 

 structure of a region little known to the geologists of this country. 

 After pointing out the primary formations of the Sierra Nevada, and 

 the recent marine strata near the southern base of the chain, be de- 

 scribes the large freshwater basins of Baza and Alhama, occupying 

 two deep depressions on its northern declivity. The strata of the 

 former basin are subdivided into two great groups ; the lower com- 

 posed of marls with many fossils of the genus Cypris, and containing 

 brine springs, gypsum, and sulphur ; the upper composed of light- 

 coloured indurated marl and limestone, charged with innumerable 

 Paludinse. The basin of Alhama gives very nearly a repetition of the 

 same phenomena : but among its indurated white marls is a larger 

 number of organic remains, some of which very nearly resemble those 

 of the freshwater limestone in the basins of Paris and the Isle of 

 Wight. 



It is not necessary for me to point out the importance of facts like 

 these j and I am not called upon to follow the author through his de- 

 tails, as his communications are already published. 



On 



