1854.] 



HAMILTON MAYENCE BASIN. 



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Between Uffhofen and 

 Eckelsheim, a short distance 

 further north, these marine 

 beds assume the character 

 of a quartzose conglomerate 

 or gravel, passing into a 

 coarse incoherent sand, and 

 the fauna is somewhat dif- 

 ferent from that of Wein- 

 heim. Here two or three 

 species of Osh'ea, including 

 the peculiar form O. rhe- 

 nana, together with two 

 species of Pecten, are almost 

 the only representatives of 

 the numerous species found 

 elsewhere. A single Pec- 

 tunculus and an Astarte 

 found in this sand were 

 so soft that it was impos- 

 sible even to touch them 

 without injury ; they crum- 

 bled to powder on removing 

 the sand. The Pectens and 

 Oysters seem to have a pe- 

 culiar facility for resisting 

 the decomposing effect of 

 the water which percolates 

 so easily through this loose 

 sand. 



II. Lower blue Brown-coal 

 Clay {Cyrenen-Mergel), 

 Cyrena-marl. 



With the exception of 

 the few hard calcareous 

 bands intercalated in the 

 shelly sands of Weinheim, 

 there does not appear to 

 have been any great change 

 in the mineralogical charac- 

 ter of the deposits formed 

 at the bottom of this ter- 

 tiary sea, so long as it main- 

 tained its true marine cha- 

 racter. Finesandandgravel, 

 derived from the disinte- 

 gration of the surrounding 

 rocks, and mixed with an 

 abundance of broken shells 

 in the upper portion, are the 

 chief materials in which 

 V 2 



