393 



Am. margaritatus beds are missing, and the Spinatus beds lie 

 apart from the main trough in a depression near Luithorst. 



THE MAEKOLDENDORF BASIN. 

 SECTION OF THE SPINATUS ZONE, MIDDLE LIAS NEAR LUITHORST 



(Dr. Emeeson). 



Near Gottingen at Northeim and Hainberge the Margaritatus 

 beds make their appearance. 



Professor U. Schlonbach, notes that in some places in this 

 part the limit between the lower Spinatus beds, and the Upper 

 Margaritatus are decidedly sharp, whilst in others the limit is 

 lost or indistinct, which is only what we should look for. The 

 characteristic Ammonites of each facies will some few live on, 

 they can surely not become extinct to a single individual at the 

 terminal range of the species ; but yielding constantly to the 

 conditions which effect mutation — conditions that are productive 

 of continuous insensible changes — it is scarcely credible that 

 individuals are all affected pari passu ; the consequence, if this 

 view be correct, would be a blending of species and an indefinite 

 limit ; no one could for a moment fancy a hair breadth Hne to 

 exist as the result of such changes ; we have mentioned before 



* I have recorded the Sphaerosiderites or Carbonate of iron, the spathose iron of PmLLrps, 

 (Phillips's Mineralogy, edited by H. T. Brookes and W. H. MiUer, 1852) from the Churchdown 

 Spinatus Zone. 



