102 H. Woodward — On a New Fossil Myriajpod. 



It may be objected that in taking the present rate at which the 

 sedimentary deposits are being formed as the mean rate for all ages, 

 we probably under-estimate the total amount of rock formed, because 

 during the many Glacial periods which must have occurred in past 

 ages the amount of materials ground off the rocky surface of the 

 land in a given period would be far greater than at present. But in 

 reply it must be remembered that although the destruction in ice- 

 covered regions would be greater during these periods than at 

 present, yet the * quantity of materials carried down by rivers into 

 the sea would be less than at present. At the present day the 

 greater part of the materials carried down by our rivers is not 

 what is being removed off the rocky face of the country, but the 

 Boulder-clay, sand, and other materials which were ground off 

 during the Glacial epoch. It is therefore possible, on this account, 

 that the rate of deposit may have been less during the Glacial epoch 

 than at present 



When any particular formation is wanting in a given area, the 

 inference generally drawn is, that either the formation has been 

 denuded off the area, or the area was a land-surface during the 

 period when that formation was being deposited. From the fore- 

 going it will be seen that this inference is not legitimate; for, 

 supposing that the area had been under water, the chances that 

 materials should have been deposited on that area are far less than 

 are the chances that there should not. There are sixteen chances 

 against one that no formation ever existed in the area. 



II. — On BuPEOBEiiiA Brownii, H. Woodw., a New Species of 



Mybiapgd from the Coal-meastjkes of the West of Scotland. 



Ey Henry Woodward, F.G.S., F.Z.S., 

 of the British Museum. 



(PLATE III., Fig. 6.) 



I HAD the honour in 1866^ to describe the first specimen of a 

 fossil Myriapod from the Coal-measures met with in this 

 country. It was discovered by the late Mr. Thomas Brown, of 

 Glasgow, an indefatigable geologist and an ardent collector of fossils, 

 who obtained it in a nodule of Clay-ironstone from Kilmaurs. 



I determined it to be identical with the Xylobius sigillarice, 

 described by Dr. Dawson from the South Joggins Coal-formation of 

 Nova Scotia.^ 



Other remains of Xylobius have also been obtained in Clay-iron- 

 stone-nodules, from the Coal-measures near Huddersfield, by Mr. 

 Joseph Tindall of that town, which were referred by me to the same 

 species, and figured in the plate with the Kilmaurs example. 



Having been in 1869 entrusted by my friend Mr. James Armstrong, 

 at that time the Honorary Secretary of the Glasgow Geological 

 Society, with another and much larger form of Myriapod from 



1 Trans. Glasgcw G-eol, Soe., 1866, vol. ii. p. 234, pi. iii. 



2 Quart. Jouru, Geol. Soc, Lend., 1859, vol. xvi., p. 268. 



