506 



J. F. BLAKE ON THE UPPER 



1. Upper Jurassic. 



I. Earrois limestone, 600 feet. 



a. Grey-green limestone. 



b. Carious limestones. 



c. Lithographic limestones. 



II. Virgulian clays, 150 feet. 



III. Astartian limestones, 400 feet. 



a. Upper compact limestones. 



b. Lower marls. 



2. Middle Jurassic. 

 I. Coral Eag, 400 feet. 



a. Lithographic limestones. 



b. Various forms. 



II. Oxford clay, 500 feet. 



a. Ferruginous oolite. 



b. Siliceous limestones = Terrain achailles. 



c. Woevre clay. 



Near the northern extremity of the department, in the neighbour- 

 hood of Dun, the lower portions of the series may be easily taken 

 up again ; and they show a continuance of the conditions last noted 

 in the Ardennes. On the slopes of the Cote St. Germain a fairly com- 

 plete section may be seen : the lower half is occupied by the Oxford 

 Clay, with the topmost part of the same nodular gritty character as 

 before ; then may be seen the Ferruginous Oolite, of some thickness ; 

 immediately over which come great crystalline irregular masses 

 which, in spite of their present state, are easily recognized as remains 

 of a Thamnastrsean reef, with which Oidaris jiorigemma occurs ; 

 this portion is also considerably oolitic, differing in this respect from 

 the limestone that follows it, which, with its vacuous spaces once 

 filled with corals and JSferincece, perfectly represents the ISTovion 

 stone. Here, then, we find confirmation of previous sections. Hebert 

 (21) states that the Coral Hag alone is seen at the base of this hill- 

 side, and that the Ferruginous Oolite must be some distance below, 

 and separated by a great mass of clay. The sequence, however, is 

 here perfectly clear ; and on the opposite side of the valley, in the hill 

 between Murvaux and Fontaines, the same succession is equally well 

 seen. Only at this spot the true Coral Rag has greatly developed, as 

 may be seen also by its examination in other places in the neighbour- 

 hood. Thus the great quarries to the south of Dun show perhaps as 

 much as 60 feet, consisting of a lumachelle of broken shells at the base, 

 a Thamnastraean reef with Ostrea solitaria in the middle, and oolite 

 beds with Cidar is Jiorigemma at the top, all of which must be about 

 on this horizon, and which give an idea of the variability of the 

 series ; while in the valley leading to Fontaines the still coral-bearing 

 upper limestones are largely developed, but without the character- 

 istic urchin of the lower reefs and their equivalents. 



Passing next to Verdun, the student who has traced the lower 



