SILURIAX KOCXS IN nERTFOEDSUIRE. 247 



the northern sea is just now brought to view ; * and in the pebbles 

 and sands which formed the shores of these two seas, or of the 

 single ocean which may have been only partially divided by the old 

 Palaeozoic ridge, we are now endeavouring to obtain a supply of the 

 purest fresh water existing within the limits of our London Basin. 



Appendix. 



I must now append a brief notice of two papers on the results 

 of the boring at Ware which have been published since this 

 paper was read before the Society. In the ' Popular Science Review ' 

 for July, 1879, will be found a paper, by Mr. Etheridge, on " The 

 Position of the Silurian, Devonian, and Carboniferous Rocks in the 

 London Area," giving much valuable information, and forming in 

 fact a most exhaustive resume of our knowledge of the subject. 

 The paper is illustrated with a map and sections. It announces, 

 for the first time, the discovery of rocks of undoubted Devonian 

 age at the jNf^ew River Company's boring atTurnford, near Cheshunt 

 (in Hertfordshire), underlying the Gault, and containing the 

 same species of fossils as were found at the Tottenham Court 

 Road boring, such as &pirifera diyuncta, Pterinea, and RhynchoneUa. 



Mr. Etheridge gives the following list of fossils from the AVenlock 

 rocks at the boring near Ware, all of which were obtained from a 

 core less than three feet in length and one foot in diameter : — 



VROTOZO k.—Ischadites Emnigi, Murcli. 



ECHINODERMATA. — Taxocrinus, sp. ; Periechocrinus moniliformis, Mill. 



ANNELIDA. — Tentaculites oruatus, Sby. 



CRUSTACEA. — Pliacops caiidatus, Briiiin. 



MOLLUSCA. — Brachiopoda. — Orthis canaliculata, Dalm. ; 0. elegantula, 

 Dalm. ; Merisiella tumida, Dalm. ; Cyrtia exporrecla, Walil. ; Spirifera elevaia, 

 Dalm. ; S. plicatella, Linn. ; Atht/ris, sp. ; Crania implicata, Sby. ; liliyuchoneUa 

 cuneata, Dalm. (?) ; Afri/pa reticularis, Linn. ; Pentamerus galeatus, Dalm. ; 

 P. linguifer, Sby. ; Strophomeim eufib/pha, Dalm. ; S. reticulata, M'Coy ; S. 

 depressa, Dalm. ; S. rhomboidalis, Wahl. ; S. antiqnata, Sby. ; Chonctes, sp. ; 

 Leptmna sericea, Sby. ; L. transversalis, Dalm. Cokchifera. — Pterinea, sp. ; 

 Mytilus mytilimeris, Conr. ; Ctenodonta , sp. ; Orthonota rigida, Sby. Gaste- 

 ropoda. — Euomphnlus rugosus, Sby. Cephalopoda. — Orthoceras attenuatum, 

 Sby. ; 0. angulation, "Wahl. 



* The shore-line of that part of the Lower Greensand sea to the south of 

 London must have run somewhere between Oxford Street and Kentish Town 

 (Prestwich, loe. cit. p. 909), for the Lower Greensand, which attains a thickness 

 of over 800 feet in the Isle of Wight, and from 400 to 700 feet in Kent and 

 Surrey, indicating a deep sea basin, thins out to 64 feet at the corner of Oxford 

 Street and Tottenham Court Road, where it has every appearance of a shore 

 deposit, and is entirely absent at Kentish Town, where the old rocks most 

 probably rose above the level of the sea. Again, in Buckinghamshire and 

 Bedfordshire the Lower Greensand has a thickness of 200 to 30u feet (as near 

 Hertfordshire as Arlesey, a few miles north of Hitchin, of at least 133 feet), and 

 at Hitchin of at least 23 feet, while at Ware it has thinned out to a few inches, 

 indicating by its conglomeratic nature, and its derived and worn fossils, a shore- 

 line of the Lower Greensand sea to the north, probably communicating in a 

 westerly direction, through Oxfordshire, with the southern sea. There is 

 some indication of the depth of this sea in the fact that the Xetherfield 

 boring, near Battle, in Sussex, was carried to about twice the depth of the 

 borings in London without the Palaeozoic land-surface having been reached. 



