Permo-Carhoniferous Ammonoids of the Glass Mountains 19 



When we compare the fauna of each of these divisions we find that 

 they may be united into two groups on account of the paleontological 

 relations existing between them. One group would be formed by 

 the Zone of Waagenoceras and that of Perrinites; while the other 

 natural group would consist of the Zone of Prothalassoceras and that 

 of Uddenites. 



The correctness of this view can be easily demonstrated for the 

 first group. We find that in both these zones occurs the genus Medli- 

 cottia; that both contain Gastrioceras belonging to the group Gastrio- 

 ceras Zitteli Gemm., and that the highly developed forms of the 

 Cyclolobinae are represented by Perrinites in the lower zone and by 

 Waagenoceras in the upper one. 



It is a little more difficult to show relations between the two lower 

 divisions, on account of the scarcity of ammonoids in the zone of 

 Prothalassoceras, but still there are some features which separate this 

 zone from that of Perrinites, and others which connect it with the zone 

 of Uddenites. Both the zones of Waagenoceras and Perrinites con- 

 tain in general quite highly developed ammonoids like Perrinites, 

 Waagenoceras, Medlicottia, Adrianites, and species belonging to the 

 group of Gastrioceras Zitteli Gemm., while both of the two lower zones 

 contain less highly developed forms. Instead of the higher developed 

 Medlicottia we find in the zone of Uddenites the new genus Uddenites 

 which is not a precursor of Medlicottia, though also a branch of Pro- 

 norites, but which has not developed in the same degree of the first- 

 mentioned genus. Instead of Stacheoceras with many lobes, we find 

 Marathonites and Vidrioceras with a very small number of lobes. In 

 the lowermost zone there occurs even the genus Schistoceras which 

 has been known only from the Pennsylvanian. In the upper zone of 

 the lower group we find a less developed member of the Thalasso- 

 ceratidae, and although the higher developed forms of this genus do 

 not occur in the zone of Waagenoceras, we shall see that in Europe 

 and Asia these higher forms occur in beds of the same age, and as- 

 sociated with forms that are also found in our highest zone. The two 

 zones of the lower group are united with each other to a certain degree 

 by the occurrence of Marathonites in both of them and they show a 

 certain difference from the zones of the higher group in the degree 

 of development of the ammonoids contained in them. 



