DORSET-SOMERSET DISTRICT. 27 
what they are made of, and also the so-called Inferior Oolite, which latter we shall 
perceive has a much more restricted meaning than with us. The following is an 
outline of their development in Normandy, abstracted from the previously-quoted 
work. Starting below the Fuller’s Earth :— 
1. The “ White Oolite.” This is said to be the normal deposit of the Inferior 
Oolite ; it is of considerable thickness, varying from twenty-eight feet to nearly 
fifty feet. The following are amongst the species quoted :—Am. Parkinsoni, dimor- 
phus, subradiatus, Martinsii, Natica Bajocensis, Trochus duplicatus, Plewrotomaria 
mutabilis, Terebratula carinata, T. Morieri, T. Phillipsii, T. globata, T. spheroidalis, 
Rhyuchonella plicatella. This may be said to form the Parkinsoni-zone. 
2. The “ Ferruginous Oolite.” This is the famous Oolite of Bayeux, or typical 
Bajocian. It is six feet thick, and divisible into three beds. The central bed is 
that in which Am. Humphriesianus, Gervillei, Brongniarti, and a crowd of Gasteropods 
occur. Above is a bed characterised by Am. Niortensis and large varieties of Pl. 
mutabilis, whilst Ter. spheroidalis is more abundant than in the middle bed. 
Finally, at the base is a nodular bed, which contains the above-quoted Ammonites 
of the horizon of Bayeux, and along with these Am. Sowerbyi, cycloides, and even 
genuine specimens of Murchisone ; most of the latter are believed to be remanié, 
This is in the main the Humphriesianus-zone, and perhaps includes in the lower bed 
the sub-zone of Am. Sauzei.' 
3. “ Mdliére,” or highest group of the ‘‘ Marnes Infra-odlithiques.” Between 
this important series of beds and the *‘ Ferruginous Oolite,” or true Bajocian, there 
is, in Normandy, a considerable hiatus marked by eroded surfaces and other signs 
of a partial unconformity. The “ Maliére” is formed of a series of beds of marly 
limestone, frequently penetrated with ‘chlorite,’ sometimes sandy and siliceous. 
The thickness varies from nine to twenty-nine feet. It frequently contains dark 
siliceous concretions. The fossils are Am. Murchisone, and especially Am. 
* aalensis”’ or ‘‘ concavus,”’ which in Normandy occurs only on this horizon. Here 
also occur Lima heteromorpha and Terebratula perovalis along with Rhynchonella 
ringens and R. quadriplicata. The characteristic Gasteropods are Hucyclus capita- 
neus and E. pinguis along with Pleurotomaria actinomphala and P. Baugieri. The 
“ Malitre ” constitutes a sort of transition between the “ Marnes Infra-odlithiques ” 
and the beds of Bayeux ; and, according to Deslongchamps, the fossils of this horizon 
were sometimes cited by D’Orbigny in his Toarcian, sometimes in his Bajocian, 
varying with the locality observed. 
It is not difficult to recognise in the “ Malitre” of the Norman geologists the 
Murchisone-zone of Dorsetshire plus the so-called Sowerbyi-zone, so well charac- 
terised by the innumerable varieties of Am. concavus. This forms the main mass 
of our Lower Division of the Inferior Oolite in Dorsetshire, is characterised 
See further on for a more detailed description. 
