560 



J. P. BLAKE ON THE UPPER 



to the beds with Trigonia spinifera at Neuvizy, and with Trigonia 

 perlata at Trouville. The first mass of importance is the limestone 

 of Houllefort, which is perfectly isolated in the midst of clays, some of 

 which separate it above from the so-called limestones of the Mont 

 des Boucards*. It is extremely fossiliferous ; bat the discovery of 

 the fossils is dependent on their weathering out, and would be very 

 unlikely in a boring. Twenty-six species are enumerated by de 

 Loriol from this limestone, and additional ones by M. Pellat. Those 

 actually noted were Trochus Jioullefortensis, Purpura sp., Oerithium 

 Struchnanni,Chemnitzia sp. (wrongly called Pseudomelania heddingto- 

 nensis), Opis Phillipsii, Area scabrella (near to A. quadrisulca), Nucida 

 cottaldina, Lima rudis, and Cidaris flori gemma. There is so much that 

 is peculiar about this fauna that it gives little help in correlation; and 

 the additional known species in de Loriol's list, e. g. Amm. plicatilis, 

 Alaria tridactyla, Pholadomya Protei and P. concinna, Trigonia. moni- 

 lifera, Lima rigida, Pecten vimineus, and Ostrea dilatata are not quite 

 conclusive. Nevertheless, on the whole, the facies is Corallian, and 

 indicates an horizon which may indeed be compared with that of 

 Neuvizy or the Osmington Oolite, but is more like the base of the 

 Corallian in the Haute-Marne and the Yonne departments. 



About the succeeding portion of the series there have been 

 several changes of opinion among the French geologists, owing 

 to there being different developments in different parts of the 

 area. The difficulties arising from this are intensified in the 

 Boulonnais by the deposits being exceedingly local and by several 

 minor unconformities occurring in the series, owing to the proximity 

 of the ancient shores. Pour localities exhibit different arrange- 

 ments, of which the sequence may be specially noted. First, in 

 the extreme north near Bazinghen there is nothing but a few feet 

 of clay between the Callovian grit with Terebratula humeralis (true) 

 and Rliynclionella varians and the Nerinaean or so-called Astartian 

 Oolite ; this is a minimum. Secondly, at the Mont des Boucards, there 

 is a maximum; but the whole is essentially argillaceous though dig- 

 nified by the name of limestone. Only at one spot on the hill-side 

 are seen a large number of loose stones scattered, on so restricted a 

 surface as to even suggest the question whether they may not be the 

 debris of ancient buildings. These stones, surrounded on all sides by 

 the clay, are probably a remanie collection, or are due to some special 

 cause which renders their actual position, at a slightly lower level than 

 the fossiliferous beds in situ, of little consequence ; but their fauna 

 is remarkable for its richness and abundance. The list published 

 and illustrated by de Loriol is very defective, including only twenty- 

 six out of eighty species which M. Pellat has, up to the present, dis- 

 covered; and half an hour's search obtained the following 30, 

 several of which are not included in de Loriol's list. Nautilus 

 giganteus, Aporrhais elegans, A. musca, Pleurotomaria hesione, Ani- 



* In his later descriptions (e. g. 56) M. Pellat places the " Calcaire du Mont 

 des Boucards " immediately above the Houllefort limestone ; but in his earlier 

 ones (e.g. 41) be recognizes that tbey are separated by a considerable mass of 

 clay* 



