516 



J. F. BLAKE ON THE UPPER 



scribed and drawn by Envignier. It shows well how argillaceous the 

 Kimmeridgian is here, being composed of quite as much clay as stone, 

 which is an exception to its usual character in France. About 40 ft. 

 is exposed ; but this does not include any lumachelles of Exogyra 

 virgula, though that oyster occurs with others. The nodular bands 

 are very fossiliferous, and include more stony beds at the base, with 

 Pholadomya multicostata, Gervillia Jcimmeridiensis, and Cucullcea 

 texta, and in more marly beds u. terocera mosensis, Trigonia Voltzii, 

 T. concentrica, Astarte scalarisl, Pleuromya Voltzii, P. donacina?, 

 Peeten suprajurensis, and Terebratida subsella. 



This description of the beds which intervene between the Corallian 

 and " Portland " limestones, though doubtless indicating that some 

 division might be adopted, does not tend to magnify the importance, 

 in this district at least, of the three groups — Astartian, Pterocerian, 

 and Yirgulian, all of which would be included in England in the body 

 of the Lower Kimmeridge. There is a community of fauna which 

 shows them all to be too intimately united for any wide separation. 

 Above the fossiliferous Virgulian marls of the Demanges cutting 

 comes immediately the unfossiliferous lithographic limestone of the 

 so-called " Portland" series, occupying all the summits of the hills ; 

 but no special observations were here made. 



3. The Uaute-Marne Department. — The development of the Upper 

 Jurassic rocks in this department has received more study and raised 

 more discussions than that in any other place. It is consequently con- 

 sidered by many the typical region in the Paris basin, and is used as 

 a term of comparison in every attempt at correlation. Lying opposite 

 the strait which connects the basin of Paris with the Jura, its lower 

 part appears to partake of the character of the Swiss rocks ; and its 

 upper part is more complete than anywhere else in the same range. 

 Although it is therefore of the highest importance that its rocks 

 should be correctly described and interpreted, the difficulties of its 

 natural situation appear to have been increased by its illustrators, 

 and one would suppose from their writings that it was of most ano- 

 malous structure. The earliest description was given by Eoyer(4). 

 Being the simplest, this was in some respects the best ; and it will 

 be well to quote it for comparison with the most recent and com- 

 plicated. Royer divides the series as follows : — 



A. Portland. ° 0LITE 0P BaRR0IS - 



a. Carious limestones. 



b. Nodular compact limestones. 



c. Lithographic limestones. 



B. Kimmeridgian. 

 0. Astartian. 



a. Nodular and oolitic beds. 



b. Compact limestone. 



D. Coralline oolite. 



E. Compact Corallian limestone. 



a. Thick limestone. 



b. Marly limestones passing to Oxfordian ; b'. Rubbly coral limestone. 



F. Upper Oxfordian marls, almost without fossils. 

 G-. Middle Oxfordian. 



H. Lower Oxfordian. 



