404 STRATIGKAPHICAL GEOLOGY 



where a few dwarfed Gryphwa and Cardinia prove the occasional 



presence of salt water. As these beds are overlain by clays with 



Oxynoticeras oxynotum, they must be the estuarine equivalents of 



the planorbe and Bucklandi zones. 



The overlying marine beds exhibit the following succession : 10 



Feet. 



3. Dark-blue micaceous clays with septaria, Belemnites acutus, 

 Platypleuroceras brevispina, Uptonia Jamesoni, Hippopodium 

 ponderosum, and Gryphcea cymbium ..... 80 



2. Micaceous sandstones and clays with Gryphcea obliquata, Pecten 



cequivalvis. and Belemnites acutus ..... 34 



1. Blue clays and impure limestones with Oxynoticeras oxynotum, 

 Arnioceras caprotinus, Bel. acutus, Cardinia hybrida, Lima 

 pectinoides, and Gryphcea obliqua ...... 60 



Middle Lias. There can be little doubt that deposits of this 

 age succeeded the Lower Lias over the whole region of the Irish 

 Sea and the Hebridean Sea, but the only remnants of them which 

 have escaped destruction are in some of the Western Isles. Here 

 they are shallow- water deposits, consisting chiefly of sandstones. 

 They are well exposed in Scalpa and Eaasay, where grey calcareous 

 sandstones, with some beds of calcareous shale, have a thickness of 

 200 feet. They contain such characteristic fossils as Amaltheus 

 margaritatus, Paltopleuroceras spinatum, Belemnites acutus, and 

 Rhynch. tetrahedra. In Mull they are represented by soft greenish 

 sandstones with few fossils. 



In Sutherland no such beds are exposed in situ, but their former 

 existence is proved by the occurrence of boulders of calcareous 

 sandstone, like those of the western coast, in the boulder-clays 

 of Moray and Elgin. These boulders enclose such fossils as 

 Belemnites paxillosus, Modiola scalprum, Pteria incequivalvis, 

 and Panopcea elongata, and others which occur in the Scalpa 

 sandstones of the west coast. It is quite possible indeed that 

 such rocks (of Marlstone age) may still exist in situ beneath the 

 vast masses of glacial clay which mantle the surface of Elginshire. 



Upper Lias. This also is only found in the Western Isles, 

 where it presents the usual shaly facies with much pyrites and 

 jet ; the lower portion yields Harpoceras serpentinum and Dumor- 

 tieria radians, and the upper beds Dactylioceras commune, with 

 Belemnites Voltzi and Posidonomya Bronni. Sections are generally 

 obscured by slips and grass, but the thickness averages from 75 

 to 80 feet. 



B. CONTINENTAL LIASSIC STRATA 



Jurassic rocks form a nearly complete ring round the great 

 Cretaceous basin of the north of France, the continuity of their 



