124 K. KEILHACK 



character, such as Trapa natans, and even Cratopleura. Such, 

 liowever, can never thrive in a flat country, if the latter is partly 

 covered with glacier ice and the climate of that country arctic. 

 Therefore a period with a warm climate must necessarily have 

 existed between the deposition of the oldest northern sands and 

 those of the ground moraine of the lower bowlder clay, and there- 

 fore for north Germany a third oldest period must be assumed 

 besides the two glacial periods which deposited the upper and 

 lower bowlder clay. The ground moraines of this oldest glacial 

 period I recognize not only in Schonen, but also in the deepest 

 ground moraines of the Baltic range, especially in that part of 

 it lying to the east of the Oder. On the other hand, no obser- 

 vations have hitherto been made which point to an extension of 

 these ground moraines in the district south of the range. 



If I attempt at the conclusion of these remarks, which I con- 

 sider necessary for the verification and defense of the stand- 

 point adopted in the official survey in north Germany, to give a 

 classification of the north German diluvial deposits in tabular 

 form, I beg that this attempt may be considered only as a pri- 

 vate opinion, which I should like to submit to a wider circle, for 

 criticism and examination. 



Preglacial. — Not yet determined with certainty. No deposits 

 between the Miocene and the first glacial epoch certainly recog- 

 nized. 



First glacial epoch. — Oldest ground moraines in the region of 

 the east Balt>c Lake district. Fluvio-glacial formations, reach- 

 in<r to Hanover, and the southern part of the Mark, e. g., the 

 sands under the deposits of the first interglacial period. 



First i?iterglacial epoch. — Clays and marls rich in Paludina 

 (Paludina deposits) in the understratum of Berlin. Peat of 

 Klinge near Kottbus. Fresh water lime of the Flaming (Belzig, 

 Gorzke, Ziesar) and of the heath of Liineberg. Diatomaceous 

 layers of the Soltau, Oberohe and Rathenow. Yoldia clay in 

 West Prussia, Cyprina clay in Holstein, fauna of Burg in western 

 Holstein, Cardium sands of Lauenburg, etc. 



