LOWER CHALK—NORTH-WEST OF FRANCE. 
255 
Followed by Gace to Mortagne the lower part of the Cenomanian 
becomes still less chalky, and passes into a yellowish, sandy, mica¬ 
ceous, and glauconitic material which resembles the Gaize de FAr- 
gonne more than any kind of chalk. Layers and scattered masses 
of chert continue to occur in it at Gace, but near Mortagne and 
Belleme they are fewer, and seem to be replaced by beds of siliceous 
limestone. 
The upper zone, or “ craie de Bouen,” consists of a greyish-white 
siliceous marl or “ tuffeau,” rather soft in the quarry, but having 
the property of hardening in the air, so that it is quarried ami used 
as a building stone. The highest part of this zone consists of beds 
of silty chalk, alternating with layers of greyish marl, more or less 
glauconitic, and containing Scaphites cequalis and Baculites bacu- 
loicles like those at a similar horizon at Bouen. 
These marls are succeeded by the “sables de Perche,” soft yel¬ 
lowish sands containing Ammonites [. Acanthoceras ] navicularis , 
Ostrea carinata, and 0. columba. 
Still further south, in the department of the Sarthe, another 
mass of sands is developed in the centre of the formation between 
the zone of Am. Mantelli and the marls with Scaphites wqualis, 
so that the succession established by M. Bizet in the communes of 
Theligny and Launay is as follows : — 
F eet. 
Sables de Perche a Am. navicularis - - - - - +20 
Craie a Scaphites cequalis , Turr. costatus , etc. - - 60 
Sables et gres a Perna lanceolata ----- 130 
Craie glauconieuse a Am. Mantelli - 80 
Glauconie a Ostrea vesiculosa - . 25 
More than 315 
Near Le Mans the whole formation has become arenaceous, con¬ 
sisting of sands with beds and masses of calcareous and ferruginous 
sandstone. 
The following is a list of the fossils which have been found in 
the several portions of the Cenomanian series near Yimoutiers. 
It has been compiled partly from the specimens obtained by Mr. 
Hill in 1895, and partly from information and specimens which 
M. Lecoeur has been kind enough to send me. The list of fossils 
obtained by him from the sand below the zone of Am. Mantelli 
has been given previously in Volume I. of this Memoir, but as so 
many of them range up into the beds above, it is repeated here for 
comparison. The last column shows those which are known to 
occur in the English Lower Chalk ; — 
