Permo-Carhoniferous Ammonoids of the Glass Mountains 7 



The chief object of our excursion, to collect as many ammonoids 

 as possible, was entirely attained; at the same time many fossils of 

 other classes were brought together, some of them from entirely new 

 localities. In the present paper I am able to describe' 29 species 

 of Permo-Carboniferous ammonoids belonging to 16 genera and sub- 

 genera. This list will certainly be much augmented by later discov- 

 eries, because on the whole the fossil treasures of the Glass Mountains 

 have been barely touched, and several months of collecting would be' 

 necessary to obtain a reasonably complete fauna from all the different 

 horizons. 



In the present publication, only the ammonoids will be described, 

 because they enable us to subdivide the enormous mass of the Permo- 

 Carboniferous sediments; while the other classes of fossils and es- 

 pecially the brachiopods, pelecypods and gastropods, are generally 

 not limited to certain horizons. To the description of the Permo-Car- 

 boniferous forms is added that of a Schistoceras from the Pennsyl- 

 vanian of the same region, on account of its relation to a Schistoceras 

 found in the lowermost Permo-Carboniferous. 



But the cephalopod fauna of the Glass Mountains is not only in- 

 teresting in so far as it enables us to establish local stratigraphical 

 horizons in the West Texas Permo-Carboniferous. Its significance is 

 much more far reaching! It enables us to correlate certain strata 

 of Central Texas and their northern continuation and it makes it also 

 possible to correlate our beds with European and Asiatic localities 

 and even may allow us to determine the relative age of several dis- 

 connected beds of Permo-Carboniferous age in different parts of the 

 earth. The lower part of our beds contains a number of cephalopods 

 entirely unknown until now, which apparently represent the oldest 

 marine Permo-Carboniferous fauna described up to the present date. 



All this will be still more emphasized when the fossils belonging 

 to other classes shall be described, but then it will be demonstrated 

 also that a fauna composed of brachiopods, pelecypods, and gastro- 

 pods may show a decidedly Pennsylvanian character and yet belong 

 to the Permo-Carboniferous and not even to the oldest part of it; an 

 observation which has been made by several other authors, especially 

 Carl Diener. 



