578 



J. F. MAKE ON THE UPPER 



There may be some difficulty in drawing a line ; hut throughout the 

 whole of the eastern and southern range one finds a marly charac- 

 ter of deposit setting in again over the true Supracorallinc beds, 

 often showing much rubble and indications of local unconformity, 

 as we should expect on the introduction of a new series. The 

 same is more remarkably true in the North and in England ; only 

 in the Boulonnais is there somewhat more difficulty in drawing 

 the line. The fossils are usually sufficiently distinct, Terebratula 

 Leymerii being a characteristic form. The conclusion, therefore, so 

 tenaciously held by Hebert (21), seems to be the true one, that these 

 beds are a part of the Kimmeridgian. The thickness of the beds 

 assigned to the Astartian by the describers of the different areas is 

 very varying. Thus, in the Ardennes they are said to be 21 feet, 

 but in the Meuse 400 feet ; on the Haute-Marne, again, they are 

 supposed to be thin. It is plain, therefore, that a large portion of 

 the 400 feet (if truly determined) must realty belong to the Supra- 

 coralline, as supposed for other reasons. Their assigned thickness 

 in the Aube is due . to a mistake, as before noted ; in the Yonne 

 again they are called 33 feet ; in the Cher, down to the base of the 

 Nerinaaan Oolito is 35 feet, though 80 feet more are included by 

 Douville. The whole is therefore of comparatively small thick- 

 ness, and forms only a subordinate portion. The Kimmeridgian is 

 thus divisible into three — Astartian, Pterocerian, and Virgulian. 

 The first of these is practically denned above. The Pterocerian is 

 adopted solely in deference to its probable justification in the area 

 where it was first introduced, namely the Jura, and to its distinct- 

 ness palaaontologically when the fossils of any locality have been 

 carefully studied. Neither in the basin of Paris, nor in any other 

 part yet studied, is it sufficiently distinct to be of much importance 

 in the field. The Virgulian is the most easily recognized Kimme- 

 ridgian deposit, because the characteristic oyster occurs constantly in 

 lumachclles ; but it is not confined to this part of the series, either in 

 an upward or downward direction. 



In the Meuse department, and probably in the Ardennes, the 

 Kimmeridgian is highly calcareous, the Virgulian portion alone 

 being marly. In the former there still remains some doubt as to 

 the true limits of the beds, and oven as to their stratigraphy. While 

 the lower portion of the Astartian requires to be added to the Coral- 

 lian, the upper group appears to represent the Pterocerian as well, 

 from the abundance, as recorded, of Pteroceras oceani, &c. The 

 lower portion abounds in the characteristic Ostrea deltoidea. As 

 Tombeck points out (40), the Virgulian must be made to include the 

 marly beds at the base of Buvignier's " Calcaire du Parrois," since 

 these contain Pholadomya acuticosta as well as abundance of 

 Exogyra virgula. In the south of the Meuse department, if we 

 place the compact limestones in the Corallian, we find the Astartian 

 well characterized as rubbly limestones : and a comparison of this 

 locality with the Haute-Marne in the valley of the Rognon, would 

 lead us to commence the Astartian above the lithographic limestones 

 which overlie the Saucourt oolite. Nevertheless it is to be noted that 



