45 



out, as left by tidal currents; the Crustaceans that pastured on them; and, 

 again, both fish and fierce Cephalopods attracted by such prey. The beds 

 in this quarry lie horizontally and comformably, except at the westward 

 end, where they are abruptly flexed or bent down by some disturbing 

 influence. Doubtless the basement bed must here drop suddenly from its 

 horizontal direction, on which supposition, the Upper Lias would follow 

 and produce a slight fault, though it scarcely merits the name. 

 The subjoined section exhibits the beds of this North Quarry : — 



I will restrict my observations on this section to the main points of 

 difference in its lithology, compared with that of the other. 



The Limestone Band, No. 3, here takes an irregular flexuose course 

 through a set of dark puce coloured shales, No. 2, and 4, which are 

 exceedingly fissile ; under the knife they cut like chocolate, and evince a 

 very argillaceous and bituminous sediment. Some of the finer clay in 

 solution has percolated fi:om above, and deposited a drab film on the surface 

 of the laminae. 



The lamination of the shales becomes more regular and perfect as you 

 approach the limestones. Simple dynamical principles fully account for 

 this phenomenon. 



An appropriate name for these shales would be the Alga Bed, albeit 

 names derived from fossils are open to objection. They contain abundance 

 of sea-weeds not imiformly distributed, but aggregated at intervals, as 

 though they had been drifted into certain hollows or gullies. Some of 

 these markings are doubtful, but others are unmistakeable and certainly 

 to be trusted. 



There are also portions of what appear to be woody or leathery stems, 

 probably of the larger fucoids, fiattened and carbonized. This part of the 

 communis zone is known in "Wurtemburg as the Al^en Banke, so styled 

 from its containing a profusion of the Algoe, many species of which are 



