OF THE PARIS BASIN. I? 



Lower Calcaire Grossier. — The Lower Calcaire Grossier 

 rests, when in its original position, on the glauconitic sands of the 

 Soissonnais, and in its lowest beds is scarcely distinguishable from it 

 — except that a bed with quartz pebbles, shark's teeth, and Eupsain- 

 mia trochijormis separates it from the underlying Sables de Cui'se 

 in a clear and constant manner. This bed can be well seen in a 

 good exposure of Lower Calcaire Grossier, at Liancourt St. Pierre, 

 near Gisors, resting on the fine sands already mentioned.* This 

 particular bed has been the cause of much controversy, some re- 

 garding it as the uppermost member of the Sables de Cuise, and 

 other authorities referring it to the base of the Calcaire Grossier. 



In certain districts, as at Abbecourt and Cuise, the transition 

 is less clearly marked, the bed of debris is absent and the junction 

 of the two formations is difficult to determine. 



Without entering into the merits of the discussion as to which 

 bed actually is to be considered as the dividing one (it is not an 

 important point), it is certain \ha.ti\\e.he.d.\\\th. Numtnulites Ixviga- 

 tus is regarded by all as typically one of the lowest beds of the 

 Calcaire Grossier, and its best development is seen in the neigh- 

 bourhoods of Soissons and Laon — the districts respectively known 

 as the Soissonnais and Laonnais. 



Near Paris, at Vaugirard and Lssy, this bed is represented by 

 a fine sandy deposit, partly calcareous and of a yellow colour, 

 often compacted into a stone (as at Festieux, Mont Ganelon and 

 LTsle Adam) full of N. loevigatus and N. scaber, and caWtd pierre 

 a Hards f by the workmen, in reference to the presence of the 

 Foraminifera, which are often of considerable size. At and near 

 Cuise this stone is well developed, and can be seen capping the 

 Cuise sands ; in some instances the stone is badly decayed and 

 detached Niimmulites can be collected in prodigious quantities, 

 while very fine sections of the chambers can be obtained by frac- 

 turing the hard portions of the limestone. The pierre a Hards 

 rests on the bed with Eupsammia trochiformis zwA Lenita patellaris. 



Characteristic mollusca of this horizon are Chlamys solea, 

 Cardiutn porulosiim and Chama calcarata. 



The "-Pierre de Sainf-Leu" is well developed in the neigh- 

 bourhood of Creil, where it furnishes excellent thick-bedded 

 building stones. At LTsle Adam, the stone is fine and hard and is 

 distinguished under the name of Roche des Forgets. At Pont-Sainte- 

 Maxence the St. Leu stone is capped by a dolomitic bed twenty- 

 six feet to thirty-two feet thick in calcareous sand with carbonate 

 of magnesium. 



At Grignon this horizon is represented by a calcareous glau- 

 conitic sand, full of Mollusca and Echinoidea. At Liancourt St. 

 Pierre, it is formed of compact beds with Corbis lamellosa, Lucina 

 gigantea, and other shells. 



* Ante, p. 12, with Section at Liancourt. 

 t Hard—?!, coin of the value of a farthing. 



