Ixxvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



The formations described by Dr. Sandberger, Prof. Beyrich, and 

 myself belong to the oldest marine tertiaries yet observed in Germany. 

 Dr. Sandbere;er refers solely to those of the Mayence basin, the di- 

 strict to which the observations in my first paper are chiefly confined. 

 The work of Prof. Beyrich treats of the tertiaries of North Ger- 

 many, extending from Silesia, the mountains of the Hartz and the 

 Tentoberger Wald, to the shores of the Baltic ; my second paper 

 refers mainly to the tertiaries in the neighbourhood of llcsse 

 Cassel. I will endeavour to point out the principal geological 

 features of these three districts, and to explain some of the points on 

 which differences of opinion still exist. I will take Dr. Sandberger's 

 '* Memoir of the ]\Iayence Basin " as m.y text for that formation. The 

 lowest member of the tertiary series in this district is the marine 

 sand of Weinheim, near Alzey. These sands repose on hard red 

 sandstone belonging to the Carboniferous formation of the Don- 

 nersberg, and lie in the hollows between several spurs of red sand- 

 stone extending in a W.N.W. direction from that mountain. Near 

 the edge of the basin they are unfossiliferous, but at the distance of 

 one or two miles organic remains are found in great abundance. 

 Here the sands become mixed with innumerable fragments of com- 

 minuted shells, and bands of hard calcareous rock alternate with the 

 shelly sand. The organic remains are purely marine. The sands 

 are overlaid by blue marls of considerable thickness, w^hich, while 

 preserving to a certain extent their marine character, show, by the 

 great preponderance of Cerithia of several species, together with 

 Cyrena, the first indications of a brackish-w^ater formation. Traces 

 of brown coal have been found in some portions of this lower blue 

 marl. Above this is a vast accumulation of limestone beds, divided 

 by the German geologists into three groups — 1st, Freshwater lime- 

 stone ; 2nd, Cerithium limestone ; and 3rd, Littorinella limestone; 

 both of which latter are characterized by the abundance of these 

 respective forms. The lower portion of the Cerithium limestone 

 contains, in particular localities, a great variety of Helices of several 

 species, besides other land shells, which have led Dr. Sandberger to 

 give it the name of fresh w^ater limestone. I cannot agree to this 

 denomination ; the brackish-water shells still pervade the whole 

 formation, and the land and other freshwater shells have evidently 

 been drifted in by rivers pouring their waters into this probably vast 

 gestuary basin. In the same way the mammalian bones found in 

 these formations have been washed in. 



These limestone beds, which abound more and more in freshwater 

 shells as we ascend, are again overlaid by a second blue clay formation, 

 containing in some districts, and particularly in the Wetterau, thick 

 deposits of brown coal, which are extensively worked. These are 

 supposed by Dr. Sandberger to be of the same age as the brown-coal 

 beds of the Wester Wald. The blue marls still contain in places a few 

 brackish-water forms, as Cyrena Faifjasii and a small Cerithium. 



In the neighbourhood of Hesse Cassel the most remarkable 

 feature is, that the blue marls and sands containing the remains of a 

 marine fauna overlie the extensive brown-coal deposits there worked. 



