254 



THE MENDIPS: A OEOLOGICArj REVERIE. 



of them cnntain LlasHic Hhells ; but Gliarlos Moore found 

 in his " microlestes quarry " great numbers of Rhoetic forms, 

 scales and teeth of fishes such as Sargodon, Lophodus, Hy- 

 bodus, and Saurichthys, and teeth of the marsupial mammal 

 Microlestftf!. Those may, however, have been washed in 

 during later Liassic times. In the Charterliouse mine he 

 found, commingled with marine shells, the freshwater 

 J'lanorbis and terrestrial molluscs, including snails and a 

 chrysalis shell. Everything points to marginal deposits in 

 close proximity to a land surface. And whereas in parts of 

 Gloucestershire, north of the Mendip axis, the Liassic strata 

 reach a thickness of something like a thousand feet, and in 

 Dorsetshire, south of the axis, a thickness of eight or nine 

 hundred feet, on the flanks of Mendip Isle Charles Moore 

 found the whole series to bo represented by some thirty feet 

 of deposit. Elsewhere, as in Vallis Vale, the Lias may be 

 wholly absent, beds of Inferior Ooh'te resting directly on the 

 Mountain Limestone, which is pierced by boring shells, and 

 has old-world oysters still adherent to the ancient rock- 

 surface. The lower Oolites tell somewhat the same tale as 

 the Lias ; for whereas they are some 700 feet thick in Dorset, 

 and nearly 5(J0 near Cheltenham, near Erome they do not 

 attain a greater thickness than one hundred feet. Mr. 

 Jukes-Brown thinks it not unlikely that there was an east- 

 ward extension of the Mendip axis forming a submarine ridgo 

 separating the Dorset basin from that of (lloucestershire. « 



In the waters of the sea around the sinking Mendip Isle 

 there wore deposited beds of clay, with a rich fauna con- 

 taining Ammonites in abundance, and masses of limestone, 

 due to the growth and waste of coral-reefs, and the acomnu- 

 lation of the remains of shell-tlsh, sea-urchins, and branched 

 sea-lilies. By such deposits wore the soas around Mendip 

 silted up ; and when the island itself was finally submerged 



