136 MESSES. A, J. JUKES-BROWNE AND W. HILL : [May 1 896, 



From the above description it will be seen that the Cenomanian, 

 which in the Calvados and in the north of the Orne consists chiefly of 

 calcareous and micaceous material, is, near Le Mans, wholly repre- 

 sented by sands with a base of glauconitic clay. M. Guillier does 

 not give the complete sequence at Le Mans in one view, but from 

 his account it appears to be as follows : — 



Feet. 



Sables superieurs a Bhynchonella compressa about 54 



Sables et gres ferrugineux a Scaphites cequalis \ „„. 



fables et gres a Trigonies et Pema lanceolata J " 



Argile glauconieuse a minerai de fer 30 to 50 



About 330 



All these sands, and part, at any rate, of the basal glauconitic 

 clay, are without doubt the correlatives of the Cenomanian of Cape 

 La Heve, as defined by M. Lennier and ourselves. In other words, 

 we do not believe that the ' Gres du Maine,' as the central group of 

 sands has been called, includes any representative of our Upper 

 Greensand, but that it is merely a littoral deposit of the age of our 

 Lower Chalk. The palseontological questions raised by this con- 

 clusion remain to be discussed. Our view of the correlation of the 

 Cenomanian deposits in the West of France and South of England 

 is shown in the Table facing p. 172. 



Y. The Minute Structure of some or the Beds in England 

 and France. 



The Cenomanian of Devon. 



In hand- specimens the gritty limestone which forms the base of 

 our zone of Ammonites Mantelli in the Devon series, and which is 

 known as Bed 10 of Mr. Meyer, presents on its fractured surface a 

 coarse, granular texture, sparkling with broken quartz-grains, often 

 as large as a pea, and with calcitic crystals ; not unfrequently, how- 

 ever, it is smoother and more compact, and sometimes seems to 

 include pebbles of a finer material. When thin sections are 

 examined under the microscope the rough, coarse-grained specimens 

 are seen to be a sand composed of shelly fragments, minute portions 

 of what seems to have been a previously consolidated deposit, 

 foraminifera, and a few sponge- spicules. Large quartz-grains, 

 some angular and some well rounded, are plentifully scattered 

 through this sand, with here and there a grain of glauconite. The 

 whole is cemented together by a clear crystalline calcite into a 

 gritty limestone. In other parts of the rock the matrix seems to 

 have been formerly a fine calcareous paste, which is now in the 

 condition of a finely granular crystalline limestone. 



As a whole, the structure of the shelly fragments is obliterated in 

 the general crystallization, and their derivation is uncertain : their 

 general outline does not suggest the prisms of Inoceramus- shells, 



