JURASSIC OF THE PARIS BASIN. 



547 



III. Normandy with Orne and Sarthe. 



1. Department of the Ome and Sarthe. — It has not been possible to 

 examine the feeble development of the Upper Jurassic rocks in the 

 narrow strip which leads northwards from Le Mans to Normandy. 

 We may note, however, that Hebert (21) shows that the Oxfordian 

 beds with Amm. perarmatus and A. cordatus, which he calls " Middle 

 Oxfordian," consist of sand and calcareous grits ; while the " Upper 

 Oxfordian," with Trigonia perlata (? " clavellata"), Pholadomya de- 

 cemcostata, Perna mytiloides, and Geryillia aviculoides, is marly. This 

 is a succession very like that to be seen near Trouville. Near Bel- 

 leme are said to be seen, over this, calcareous grits full of Trigonia 

 Bronnii (surely not the Supracoralline species !) ; next some oolitic 

 limestones, with large Astarte mysa (?=A. ovalis). Next come piso- 

 lites with Nerinoece (probably equivalent to the limestones of Trou- 

 ville and Osmington); and finally, at some distance above, come 

 Diceras-beds, containing Cardium corallinum and Corbis gigantea, 

 which have not been matched further north. These Diceras-beds 

 elsewhere in the neighbourhood are said to be covered by an oolitic 

 coral-limestone, very irregular on its surface. This is succeeded by 

 marls and marly limestones, with Ostrea deltoidea and several other 

 of the lower fossils of Havre, such as Trigonia Meriani (" muricata "), 

 Cyprina cornuta, and Khynchonella inconstans (?) ; and after a very 

 slight interval come the Virgulian marls. These facts are very in- 

 structive, as showing, amidst a general development similar to that 

 of Normandy, some of the peculiar features, e. g. the Diceras-beds, 

 of the great southern range. 



2. Normandy. — In studying this district it will be well to go, in 

 the first instance, to the coast, because there the section is complete 

 and has been described by several authors. The earliest description 

 was that by Caumont (1), who gives some account also of the inte- 

 rior, and recognizes the following subdivisions : — (1) Kimmeridge 

 Clay, (2) Glos sand and Blangy limestone, (3) Coral Hag, (4) Oxford 

 Clay. A later and more complete description of the coast only is by 

 Hebert (28), who gives very detailed sections, and divides the rocks 

 studied into (1) Coral Hag, (2) Upper Oxfordian, and (3) Middle 

 Oxfordian. A further description of the higher rocks was promised 

 at the time, but has never yet seen the light. The continuation 

 of the series on the opposite side of the Seine, at the Cap de la 

 Heve, has been described by Dollfus (30), who recognizes three 

 portions of the Ximmeridgian, as (1) Ammonite-clays, (2) Pteroceras- 

 marls, (3) Trigonia-clays and limestones ; and by Lennier (49), who 

 gives a detailed section of the beds at the Cap de la Heve, and 

 thence to Octeville. 



In the examination of this section the English geologist is at 

 once struck with the extraordinary resemblance of the series to those 

 at Weymouth and Osmington. So close indeed is it, that almost bed 

 for bed can be recognized ; and the whole becomes therefore an admi- 

 rable term of comparison between the French and English rocks, 



2 o 2 



