524 



J. P. BLAKE ON THE UPPER 



beds ; but the whole corresponds to the marls below. Though nothing 

 is seen above these Oxfordian rocks on the left bank of the Aube, 

 the whole country on the right bank to near La Mothe is occupied 

 by limestone rocks very similar in character to those at Buxieres, 

 though only occasionally observable. At La Mothe itself the most 

 characteristic rock is exactly of the Doulaincourt and Buxieres type, 

 and totally unlike any thing called La-Mothe Oolite elsewhere ; 

 beneath it is a thick mass of large-grained oolite (perhaps 30 feet), 

 worked for building-stone at Curmont, below which here, in an exca- 

 vation, are seen the shelly limestones as at Buxieres. The succession 

 is exactly the same, and the fossils similar. 



In Eoyer's first description (4) these Diceras-beds were placed on 

 the same level ; and it was after his visit to the valley of the Yonne, 

 where two Oolites are developed, that he endeavoured to find two 

 also in the Haute Marne. The Oolite at La Mothe lies on a mass of 

 compact limestone, which he traced to Soncourt, and there found 

 rubbly beds at the base. These rubbly beds he apparently took 

 for the thinned representative of the whole of the Corallian. 

 Numerous sections seen and described show that (as at Buxieres) 

 the base of the Corallian is rubbly and Coralliferous ; but it has 

 never been proved that the Oolite of La Mothe overlies any such 

 beds as the rubbly and oolitic limestones which cap the Diceras- 

 beds at Buxieres ; on the contrary, such beds, with their usual 

 Brachiopoda, are seen above the Oolite in the neighbourhood of La 

 Mothe ; and these are followed by compact, almost lithographic lime- 

 stones ; but whether immediately or not cannot be certainly made 

 out. Above these come the irregular limestones which usually in- 

 dicate the Astartian zone ; and on the hill of Colombey-les-deux- 

 Eglises are the marls full of Exogyra virgula, the whole being very 

 parallel to what is seen above Saucourt. The difference in elevation 

 between Curmont and Colombey is about 150 feet. 



On the undisputed Astartian and Virgulian of the Haute Marne 

 no special observations have been made ; but it may be noted that 

 the Geological Society of France found in the rubbly limestones of Don- 

 jeux, associated with several Nerincece, Natica hemisphcerica, iV. turbi- 

 niformis, Pholadomya Protei, Plectomya rugosa, Ceromya excentrica, 

 C. obovata, Exogyra virgula, Ostrea solitaria, Rliynchonella pinguis(?), 

 Terebratula subsella, T. Leymerii, and Holectypus corallinus. Prom 

 Joinville northwards we have the most complete development within 

 the basin of the " Portland " rocks. At that town great masses of 

 lithographic limestones are quarried, all with the peculiar clay bands 

 dividing them into thin blocks, and containing virgulian lumachelles 

 here and there. They have a great thickness, and are very unfos- 

 siliferous ; there are some alternations of marls and earthy lime- 

 stones, and a block of oolite at what may be conveniently called the 

 top. The Ammonites that have been found in them — A. gigas, A. 

 suprajurensis, and A. rotundus, together with Trigonia Pellati, T. 

 Cottaldi, Cardium Foucardi, Myacites jurassi, Pecten suprajurensis, 

 with others recorded by Tombeck, are sufficient to correlate these 

 limestones with what has been known elsewhere as Lower Portlan- 



