Vol. 52.] A DELIMITATION OF THE CENOMANIAN. 135 



4. Sarthe. 



Proceeding still southward, we find that the next change takes place 

 in the lower portion of the Craie de Rouen, which becomes sandy 

 and passes into grey sands with blocks of calcareous sandstone. 

 Thus in the communes of Theligny and Lamnay a mass of such 

 sand is intercalated between the ' Craie a Scaphites ' and the ' Craie 

 glauconieuse a Ammonites Mantelli. 9 The researches of M. Bizet in 

 this district have established the following succession : — 



Feet. 

 5. Sables du Percbe a Ehynchonella compressa, with Ammonites 



navicularis and Trigonia +20 



4. Craie a Scaphites agualis, with Ammonites varians, Turri- 



lites costatus, and Pecten asper 60 to 70 



3. Sables et gres a Perna lanceolata et Anorthopygus orbicularis 130 

 2. Craie glauconieuse a Ammonites Mantelli, Turrilites tuber- 



cidatus, Pecten asper, etc 80 



1. Glauconie a Ostrea vesiculosa 25 



+325 



Finally, towards the south-west, in the direction of Le Mans, the 

 •* Craie a Scaphites ' also undergoes a lateral change ; beds of sand and 

 sandstone set in, and the chalky marls thin out, till the whole is 

 replaced by sands of various colours, grey, green, and yellow, 

 enclosing large blocks of calcareous sandstone. These sands have 

 yielded a large number of fossils, the numbers known to H. Guillier 

 in 1886 being, of mollusca 200 species, of echinodermata 30, of 

 bryozoa, corals, foraminifera, and sponges over 130 species. The 

 larger number of d'Orbigny's types were in fact obtained from this 

 portion of the Cenomanian series. 



The ' Sables a Anorthopygus orbicularis' maintain their characters 

 and thickness below the ; Sables a. Scaphites' and have also yielded 

 many of the same fossils. 



The Craie glauconieuse, however, partakes in the prevalent 

 change, losing its calcareous ingredient, and passing into beds of 

 fine micaceous sand and ferruginous clay, so different in appearance 

 from Craie glauconieuse that they might have been referred to a 

 lower horizon, were it not that they contain in places some of the 

 characteristic fossils of the zone of Ammonites Mantelli, such as 

 Ammonites Vibrayeanus, A. falcatus, and A. rotomagensis. 



As regards the ' Glauconie a, Ostrea vesiculosa ' M. Guillier 

 remarks : — ' In the west of the department there exist beds of 

 glauconitic material which seem to be the prolongation of these, but, 

 as they do not contain fossils and are intimately united with the 

 overlying beds (argile glauconieuse a minerai de fer), we have not 

 separated them.' Clearly some further investigation of these beds is 

 required, and we may hope that the survey of the Sarthe on which 

 M. Bizet is now engaged will enable him to determine whether the 

 O. vesiculosa-beds die out entirely, as we should think most probable, 

 or whether some representative of them really does occur at the 

 base of the ferruginous clays. 



