JURASSIC OF THE PARIS BASIN. 



513 



pisolitic, stated to be 300 feet in thickness *; and above them occur 

 150 feet ofoolitic beds with various -sized grains, some pisolites,nodules, 

 and many specimens of Diceras. The whole of this mass is considered 

 by Prof. Hebert to be above the white limestones of Novion and 

 Verdun, which would place them in the Astartian of Buvignier, but 

 that he considers them to be absolutely wanting to the north of St. 

 Mihiel. Prom their position in relation to the great crinoidal 

 limestones of Lerouville, however, not 1800 yards away, their lower 

 portion can be nothing else than the jSTovion limestone ; and we 

 learn that at this spot the peculiar pisolitic character of the Diceras- 

 beds begins to be observable in this portion of the series towards the 

 top. It is remarkable that no mention is made of this in Buvignier's 

 work, though the spot is coloured as Corallian. The next cutting, 

 2j miles to the west, is also described by Prof. Hebert. Here the 

 base is occupied by the same pisolitic Diceras-beds, their continuance 

 being accounted for by some folds and reversed dips observed. This 

 bed is declared by Buvignier (22) to be distinct from that at Vadon- 

 ville, and to belong to the pisolites he has described from the Astar- 

 tian. His description, however, of the cuttings is by no means clear 

 (13), while Hebert's is precise and definite. Above these pisolitic beds 

 come a few feet of oolites, and then a mass of non-oolitic marly 

 limestone with conglomerates and Ostrea deltoiclea. The same series 

 of cuttings reveal Yirgulian beds further to the east at Loxeville, 

 with many fossils common to the Astartian beds, and, finally, the 

 lithographic " Portland " f limestones (see 21). This is well-deve- 

 loped in the neighbourhood of Bar-le-Duc, forming the main mass of 

 the hills. The carious limestones above are well-marked, with their 

 hollow tubes filled with a brown earth. This is supposed by Tom- 

 beck to be the original material, and the limestone to have formed 

 afterwards ; but this can scarcely be the case, as there are in this dis- 

 trict many fossils in the limestone with their interiors formed of the 

 matrix but the shell gone. The assemblage of these appears to in- 

 dicate very shallow-water conditions, as though here one were at the 

 natural boundary of the deposit; they are mostly small and simple. 

 Those found are Maria dionysea, Mactromya rugosa, Plectomya 

 rugosa, Lucina aspernata, Corbicella Moreana, LitJiodomus vietus, 

 and Oardium pesolinum ?. We have very little assistance here to- 

 wards correlation with our English rocks, and none towards placing 

 these on a level with the Portland Limestone. 



The highest beds seen here are a variable series of rather dirty- 

 coloured stones with sands &c. ; but one remarkable rock requires 

 special notice. It is the " vacuolar oolite," in which, so to speak, 

 there are no oolitic granules, though once there were ; each granule 

 has been dissolved, the intervening matrix alone remaining to form 

 a spongy rock. This becomes in places almost a lumachelle of Corbula 



* The thicknesses given by Prof. Hebert are always very large when estimated, 

 and require to be somewhat reduced to bring them into comparison with the 

 estimates of other geologists. 



t The names used by the describers are adopted until the amended nomencla- 

 ture is proposed at the end of this paper. 



Q. J. G. S. No. 148. 2 ii 



