1854.] HAMILTON — MAYENCE BASIN. 295 



changes which first produced and then cut off the communication be- 

 tween the Mayence basin and the German Ocean. 



The Mayence beds rest immediately on the older formations of 

 the New Red Sandstone, the " Rothe-todte-liegende " of the Germans. 

 We may therefore conclude, that during the Cretaceous and earlier 

 tertiary periods this portion of the country was dry land, sloping gra- 

 dually to the southward from the mountain-districts of the Hunds- 

 riick and tbe Taunus, until it met the southern ocean in which the 

 "Flysch" was being deposited, off and around the group of islands 

 which formed the nucleus of the Alpine chain, now such an impass- 

 able barrier between the Mediterranean and the North Sea. This 

 depression or gradual sinking continued, affecting in all probability, 

 to a certain extent, the neighbouring continent, until it reached such 

 a point, aided to all appearance by other local depressions, as to 

 occasion the formation of that remarkable valley of the Upper Rhine 

 from Basle to Mayence and Bingen, and opening to the eastward 

 round the Taunus into the German or Northern Ocean. 



There, in a bay of this newly opened sea, were deposited those beds 

 now under consideration, which, while partaking of the quasi-tropical 

 character of the Mediterranean, also combined many forms peculiar 

 to that ocean which had long existed to the north of the Hundsriick and 

 the Eifel, occupying the site of Belgium and the north of France, 

 and depositing the various forms of the Eocene period. With such a 

 change as this, however, new conditions of life must have been intro- 

 duced. The volcanic agency exerted in many places rendered these 

 waters for a time unfit for animal life. The deposits on the various 

 coasts were modified and changed, new river-channels were formed, 

 while old ones were blocked up, and species which could only exist 

 under the former circumstances necessarily disappeared, while others 

 adapted to the new conditions were introduced. 



As far as has been hitherto observed, the animal whose remains 

 have been found in the lowest portion of the Marine Sands of the 

 Mayence beds is the Halianassa Collinii, associated with the nume- 

 rous teeth of one or more species of Lamna. Now, we do not find 

 Halianassa Collinii anywhere amongst the Belgian fossils ; but it 

 has been found in a portion of the Vienna basin, in Switzerland, and, 

 if I am not misinformed, at Malta ; thus showing a connection at 

 this period between these beds and the southern or Mediterranean 

 ocean. But this remarkable animal, of Avhich the perfect skeleton 

 was lately found in the sands of Uffhofen (page 264), does not occur 

 in the upper beds ; it may thence be inferred that soon after the 

 opening of this channel, and bef(;|^e the more torpid and slowly 

 moving Molluscs had reached a distance which the Sharks, &c. had 

 rapidly traversed, the subsidence of the Alpine region, indicated by 

 the vast thickness of the " Flysch " beds, had ceased, and, in com- 

 pliance with that law of oscillatory movement, which appears in former 

 periods to have been so universally prevalent on the surface of our earth, 

 had been succeeded by an upward movement, which extended so far 

 as to cut off the connection with the Mediterranean, leaving open only 

 that with the northern and Belgic ocean. This continued for a long 



VOL. X. — PART I. Y 



