D. C. Davics—The Millstone. Qrit of North Wales. 123 



But .asHuining tliattlioso Grit beds owo tlioir orif^iii to ilio (lostruc- 

 tion of old wostovn lands, it will bo koou that a considora1)lo amount 

 of sorting of the materials (l)Oth nieehanically and clicinicalJy) would, 

 bo required before those Sandstone beds could bo deposited so com- 

 paratively free from extraneous matter as wo now find. them. The 

 whole mass must have been sifted and re-arranged according to its 

 gravity, bulk, chemical affinities, depth of water, etc. That thcso 

 conditions havo often changed on tho same spot, is shown by tho 

 frequent alternation of bods of clay, shale, and sandstone. Great 

 quantities of the lighter fclsi)athic mud would be caiTied further out 

 to sea, and may, probably, now exist as fine sedimentary deposits 

 beneath the Coal Measures of tho Shropshire and Cheshire plains. 

 Is it out of place to imagine that in these lie buried the Encrinite 

 beads, whose stems alone remain in tho Sandstone beds of the 

 Millstone Grit ? 



Fossils of the Millstone Grit of the North Wales EorcZer.— Judging 

 from its appearance elsewhere geologists have generally considered 

 the Millstone Grit devoid of fossils ; a sandy Lybian desert by the 

 side of the teeming life of the limestone rocks. Thus, in an interest- 

 ing book, written by the late Mr. George Eoberts, of Kidderminster, 

 it is stated, " Bands of drifted plants in layers distinct from the rock 

 are found in its Upper Measures, with this exception — the Millstone 

 Grit is void of fossils, and has only to be studied for its mineral 

 character." Very recently the Eev. Charles Kingsley has reiterated 

 this statement in one of his papers, in "Good Words for the Young." 



In the year 1860, however, I communicated a paper to the 

 Oswestry Field Club, announcing that the sandstone beds of this 

 formation had been redeemed from this charge of barrenness, and 

 some years afterwards, Mr. Pressor published an account, in the 

 Geological Magazine, of the fossils they had yielded to his 

 researches.^ The principal fossils are enumerated with the Sweeney 

 section, and it will not be necessary to recapitulate them here, except 

 to say that further north, in "Allinson's quarry," south of the 

 Oswestry Kacecourse, and in the " Forest Quarry," north-west of 

 the same place, to the fossils in the upper beds may be added, 

 Spirifera bisulcata, Bellerophon, a small Strephodes, Streptorhynchus 

 crenistria, in several varieties, fragments of Trilobites, and an abun- 

 dance of an uncertain species of Athyris, that continues to be plentiful 

 northwards by Selattyn Tower. 



In addition to the ever-present Productus semireticulatus, there are, 

 in the top cherty beds of Allinson's quarry, P. undatus (var. eleyans), 

 P. costatus, and P. Yoimgianus. 



The fossils are found in nests or colonies, in spots which we may 

 suppose, from the unbroken appearance of their shells, were favour- 

 able habitats for the fauna of the period. 



The most abundant fossil is Productus semireticulatus, var. Martini, 

 which is to be found by hundreds within a yard of the topmost beds 

 in the Sweeney section, and is found also in the red and yellow beds 



1 " The Fossiliferous character of the Millstone Grit at Sweeney, near Oswestry, 

 Shropshire," by W. Prosser, F.G.S., Geol. Mag., 1865, Vol. II., p. 107. 



