196 PKOCEEDmGS OP THE GEOLOGICAL SOCIETT. [Jan. 25 



4. Subsequently by increase of rainfall or decrease of beat, the 

 waters again comparatively freshened, but stiU remained salt, a fact 

 proved by the occurrence of pseudomorphous crystals of salt in sandy 

 layers interstratifled with the marls, up to, and even in, the recog- 

 nized Ehsetic strata. Gypsum also occurs above the bone-bed. 

 These circumstances may be accounted for by the close relation of 

 the Ehsetic beds to the ordinary marly series. That Ehaetic areas 

 got dried by temporary isolation seems certain; for sun-cracks 

 have been observed in the strata by Mr. Bristow, and also pseudo- 

 morphous crystals of salt. 



5. During the deposition of the upper part of the Keuper marls, 

 overlaps took place of upper across lower strata. This would 

 necessarily take place in any deep wide lake-basin first half 

 drained by mere evaporation, and again, by a change of conditions, 

 gradually filled with water from which sediments were being depo- 

 sited across a broader area. 



FoT example, were the rainfall of the area drained by the Jordan 

 to increase gradually, the basin of the Dead Sea would by degrees 

 fill with water, and successive deposits of sediment would gradually 

 everlap each other on the shelving slopes of the lake-basin in which 

 solid salts had previously been deposited. There are examples of 

 this kind of overlap in the Kew Eed Marl of England, in Somerset, 

 Gloucester, Hereford, and Leicester shires. 



6. In the British area, sinking of the district took place at or about 

 the time when the lake or lakes got nearly filled with sediment ; and 

 the same may have been the case in other European areas. A 

 partial influx of the sea took place over shallow bottoms ; and the 

 marine life that accompanied it, and the deposits that ensued, to- 

 gether form the Ehsetic beds of England. These marine forms 

 migrated from a true Eheetic ocean, in which the Lower St.-Cassian 

 and Hallstatt beds were deposited. If the Dead-Sea area, by increase 

 of rainfall, got filled up, and if depression of land took place so as to 

 admit the waters of the Eed Sea or Mediterranean, analogous 

 results would ensue ; for a marine or estuarine fauna would be 

 superimposed in shallow water, on a set of strata containing salt in 

 certain lower deposits. The Dead Sea, like the Keuper, is singularly 

 destitute of remains of aquatic life. 



Under these conditions, it is evident that the thin Ehsetic beds 

 of North-western Europe might have been deposited in great part 

 in shallow seas and in estuaries, or in lagoons, or in occasional salt 

 lakes of small or great dimensions, separated from the sea by ac- 

 cidental changes in physical geography. Many years ago, while at 

 Lyme Eegis, the late Professor Edward Eorbes stated to me that the 

 fauna of the White Limestone, at that time called White Lias, 

 reminded him, in its assemblage of forms, of the fauna of the Caspian 

 Sea ; and this seems to be a case in point, though not in all respects 

 strictly analogous*. The fauna of the Caspian is very small in 



* Mr. Moore, speaking of the " White Lias," considers that " the general cha- 

 racter of the deposit is such as we might expect to find in a lagoon or inland sea 



