1871.] KAMSAT — LOWEK LIAS. 191 



known that the peroxide of iron, as a thin pellicle, only inerusts the 

 grains of sand that form the New Eed and other red sandstones ; 

 and microscopic examination of the New Eed Marl proves that 

 the grains or flakes of sandy mud composing it are encased ia 

 the same manner*. Both Sandstones and Marls, I believe, have 

 been formed in lakes, and their red colour is connected with this 

 circumstance ; for it seems impossible that an oxide of iron could 

 be deposited from solution in an open sea in sufficient quantity 

 to colour sediments red, though common pink mud might be so 

 formed from the mechanical waste of red granite or other rocks. 

 The remains of land-plants in the Keuper series, and the peculiarities 

 of some of the reptUes of the period, tend to confirm the view that the 

 strata were deposited in inland salt lakes. Their footprints prove 

 that they walked over moist surfaces ; and if these surfaces had been 

 simply left by a retiring tide, they would generallj have been obli- 

 terated by the returning flood, in the manner that we see every day 

 on our own sandy shores. It seems to me that the surfaces on which 

 we now find fossil footprints were probably rather left bare by the 

 summer evaporation of a lake ; these surfaces were baked by the sun, 

 and the footprints hardened, so as to ensure their perpetuation, before 

 the rising waters brought by flooded muddy rivers again submerged 

 the low flat shores and deposited new beds of silt, just as they do at 

 the present day round the Dead Sea and the Salt Lake of Utah. 



The Foraminifera of the Keuper Marls, which are numerous, 

 might just as well have lived in a salt lake as in the open sea f; 

 and the same may be said of Estheria minuta. The single flsh 

 of our Lower Keuper Sandstone, Di/pteronotus cyphus, will fall under 

 the same category. The Microlestes antiquus, which occurs in the 

 bone-beds of Stuttgart, and in the Red Marls of Watchet, in Somer- 

 setshire, according to Mr. Boyd Dawkins J, proves nothing except 

 that there was land in the vicinity. 



* Mr. Ward, of the metallurgical laboratory, Jermyn-street, at my request 

 discharged the coloiir from fragments of New Eed Sandstone and Marl by an 

 acid solution of protochloride of tin. Both became white. Under the micro- 

 scope the marl appeared as a very fine-grained sandstone composed of perfectly 

 white minute fragments of silica. In both the grains had evidently been simply 

 coated with a thin pellicle of peroxide of iron. In the sandstone the peroxide 

 of iron was r89 per cent. 



t Species of Foraminifera are exceedingly variable in form ; and many of 

 them have a long range in geological time. They are therefore of little value 

 in helping to the determination of stratigraphical horizons. It may be true, for 

 example, that if the Chalk were entirely composed of Foraminifera it might be 

 difScult to distinguish from deposits now forming in the Atlantic ; but if these 

 Atlantic deposits were, like the Chalk, half consolidated, heaved up, and denuded, 

 geologists would not feel at a loss regarding their age. They would miss, in the 

 first place, all the genera of Cephalopoda characteristic of the Chalk, besides 

 numerous peculiar genera and species of Echinodermata, and, perhaps with one 

 exception, all the species of Brachiopoda common in the Chalk. Further, over 

 large areas, they would be apt to find Tertiary strata of various ages intercalated 

 between the Old and New Cretaceous beds, which would at once furnish a clue 

 to men experienced in field geology. 



I Mr. Dawkins considers that these strata belong to the Kheetic beds ; but the 

 marine Eihatic fossils have not been foujid so low. 



p2 



