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. Parldnsoni, dimor- 

 phus, subradiatus, Martinsii, Natica Bajocensis, Trochus duplicates, Pleurotomaria 

 mutabiliSfTerel ■■ T M ' ' '" Philfy \i,T globata, T. spJiceroidalis, 

 Rhynchonella 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. Ew h ' ,G '" '. " ' 'Hi, andacrawdof Gasteropods 

 occur. Above is a bed characterised by Am. NioHcasis and large varieties of PI. 

 mutabilis, whilst Ter. sphceroidalis 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 Murchisona ; most of the latter are believed to be remanie. 

 This is in the main the Humph ■ ' -one, and perhaps includes in the lower bed 

 the sub-zone of Am. Sauzei. 1 



3. "Meniere," or highest group of the " Marnes Infra- oolithiques." 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 " Maliere '' 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. Murchisona, 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 B. quadriplicata. The characteristic Gasteropods are Eucyclus capita- 

 neus and E. pinguis along with Pleurotomaria actinomphala and P. Baugieri. The 

 '* Maliere " constitutes a sort of transition between the " Marnes Infra-oolithiques " 

 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 " Maliere " of the Norman geologists the 

 Murchisona-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 

 1 See further on for a more detailed description. 



