1855.] HAMILTON — TERTIARIES OF HESSE CASSEL. 139 



would by altering the conditions of life be sufficient to cause a con- 

 siderable modification in the organic remains, without referring the 

 beds to distinct epochs. I have also stated that Prof. Sandberger 

 identifies the Westeregeln Sands with the Weinheim Sands, and the 

 Septaria-clay of Brandenburg with the Lower Cyrena-marl of the 

 Mayence basin. Now this Cyrena-marl contains a great admixture 

 of brackish-water forms, while nothing of the kind is found in the 

 Septaria-clay of the north of Germany. The change in the Mayence 

 basin is a purely local one ; and there is, therefore, no evidence of its 

 being contempot'aneous with the Septaria-clay. It is true the Cyrena- 

 marl overlies the Weinheim Sands, as the Septaria-clay overlies the 

 Westeregeln Sands ; but that is no proof of identity of time, the 

 changes in the two localities not being owing to the same causes ; 

 and Prof. Sandberger has himself shown, in the lists which he has 

 published (op. cit. p. &7), that the Marine Fauna of the Cyrena- 

 marl has the greatest affinity with that of the Middle Limburg 

 formation, the very same Belgian bed with which he had already 

 identified the Weinheim Sands. I am therefore disposed to look 

 upon the whole marine fauna of the Mayence basin as referable to 

 one period, viz. the Middle Limburg, locally modified in its upper 

 portion by the introduction of vast bodies of fresh water, or by its 

 gradual separation from oceanic influence, by which the waters be- 

 came brackish, and its organic contents more and more modified, 

 until at length all traces of marine or brackish-water fauna disap- 

 peared. 



With regard to the Cassel marine beds, I consider them as forming 

 a portion of the same marine deposit, and constituting a link in that 

 connection which must have existed between the Mayence basin and 

 the Northern Ocean. Here again we find two petrographically 

 distinct beds, viz. blue clay or marl and shelly sands ; but in this 

 case the marls underlie the sands. In one locality, near Ober Kau- 

 fungen, Septaria are abundant in the blue clays ; in others they are 

 wanting. In this locality the overlying sands are full of marine shells, 

 while near Landwehrhagen the sands which overlie the blue marl 

 containing marine shells, are entirely devoid of organic remains. 

 These are evidently mere local differences, such as may be observed 

 on any coast at the present day. 



It is also worthy of notice that the marine beds in the neighbour- 

 hood of Cassel are of no great thickness. This was no doubt owing 

 to the earlier upheaval of the underlying secondary formations (pre- 

 ceding the volcanic outbursts), which were ultimately raised to an 

 elevation of more than 1000 feet above the sea, north of Cassel. 

 This upheaval cut off all communication with the northern Ocean, 

 and confined the waters to the Mayence basin, thereby exposing 

 them to the influence of the freshwater rivers, and producing that 

 brackish- water condition which we have already noticed. 



In the great district which forms the low undulating lands of the 

 north of Germany, to the north of the Hartz and of the other moun- 

 tain ranges which extend towards the Weser Bergland, and thence to 

 the Haarstrang on the Ruhr, east of Cologne, the marine condition 



