196 EEV. J. F. BLAKE ON THE 



the land in the direction of Worborrow. In the lowest 28 feet of 

 shales I have found Ammonites alternans associated with Exogyra 

 virgida and Am. hiplex. We are therefore fairly in the Lower Kim- 

 meridge, but not at its base ; and we learn that all the series is here 

 more or less shaly, as it was in the sub-Wealden boring. Now if we 

 add all these ascertained measures together, we find just 1100 feet 

 between the base of the Portland Stone and the lowest part of the 

 Kimmeridge Clay visible, which is not, however, its base. It seems 

 absurd to suppose that with this enormous thickness any part of 

 the series should be absent, and that such member should be found at 

 Boulogne, where the total thickness between the Portland and Coral- 

 lian is less than 450 feet. We should rather expect that any division 

 found at the latter place would be expanded to twice its amount ; 

 and it is with such an idea that we must seek out equivalents. The 

 fact is that in England we possess the normal formation, to which the 

 name Kimmeridge was originally applied; while at Boulogne we find 

 an episode having no relation to the Portlandian above, but to which 

 the name of " Boulognian" may well be given. The episodal cha- 

 racter may be easily seen in the cliffs on either side of the town, 

 where conglomerates are found, and an actual dying off beneath the 

 Fort du Mont de Couple. 



It is beyond the scope of the present paper to notice the succes- 

 sion here any further than it may throw light on our English equi- 

 valents. The upper part of their "Middle Portlandian" is our 

 Portland Sand ; as M. Pellat states, it is more sandy than the shales 

 below, and has the aspect of the St.-Alban's beds with their small 

 nodules ; it contains such leading fossils as Mytilus autissiodorensis, 

 Pecten Morini, Avicula octavia, Astarte scalaria, Lima holoniensis, 

 Perna BoucJiardi, Pecten lamellosiis, Astarte Scemanni. This amounts 

 to 57 feet, which is not a quarter of the corresponding beds at St. 

 Alban's. The lower part of their " Middle Portlandian " consists of 

 soft sandy marls and shales, with cement-stone bands, not at all unlike 

 the top of the Kimmeridge at Chapman's Pool. The Cardium mori- 

 nicum (or, as I previously called it, G. striatulum), Belemnites 

 Souichii, and Piscina latissima serve to prove the identity. 



Eef erring to my section on the Kimmeridge coast*, in Nos. 1 to 9 

 I have traced three bands of fossils. ~No. 5 contains abundance of 

 Pentalium Quenstedti, apparently not yet found at Boulogne. No. 7 

 has a species of Alaria, perhaps A. cingulata (Koch & Dunk.), which 

 occurs also in the Lower Kimmeridge; and No. 9 is full of Piscina 

 latissima. These last two occur in the same order at Boulogne ; but 

 the comparative thicknesses of the deposits are 2^2 feet in England 

 and in France 44 feet. We are thus forced to look for the normal 

 representatives of the Boulognian episode in the beds from No. 10 

 downwards of my section. The place of occurrence of this episode 

 is not so far removed but that we may hope to trace some mark of 

 its occurrence at Kimmeridge; but the fossils, being mostly " co-va- 

 riants," will yield us little assistance. The general character of the 

 deposits at Boulogne is as follows : — There are three more ferru- 

 ^ Quart. Journ. Geol. Soc. vol. xxxi. p. 198. 



