W. Carruthers — Revleiv of Fossil Botany. 461 



This contrast is strikingly seen between the conformable series of 

 less than 2000 feet of strata which in Scandinavia are characterized 

 by the first three Palgeozoic faunas (Cambrian and Silurian), and the 

 repeatedly broken and discordant succession of more than 30,000 

 feet of sediments,^ which in Wales are their paleeontological equiva- 

 lents. It must, however, be considered that in regions of small 

 accumulation where, as in Scandinavia, the formations are thin, there 

 may be lost or unrepresented zoological epochs whose place in the 

 series is marked by no stratigraphical break. In such comparatively 

 stable regions, movements of the surface sufficient to cause the ex- 

 clusion, or the disappearance by removal, of the small thickness of 

 strata corresponding to an epoch, may take place without any con- 

 spicuous marks of stratigraphical discordance. 



The attempt to establish geological divisions or horizons upon 

 stratigraphical or palgeontological breaks must always prove falla- 

 cious. From the nature of things, these, whether due to non- 

 deposition or to subsequent removal of deposits, must be local ; and 

 we can say, confidently, that there exists no break in life or in sedi- 

 mentation which is not somewhere filled up and represented by a 

 continuous and conformable succession. Wliile we may define one 

 period as characterized by the presence of a certain fauna, which, in 

 a succeeding epoch, is replaced by a different one, there will always 

 be found, in some part of their geographical distribution, a region 

 where the two faunas commingle, and where the gradual dis- 

 appearance of the old before the new may be studied. The division 

 of our stratified rocks into systems is therefore unphilosophical, if 

 we assign any definite or precise boundaries or limitations to these. 

 It was long since said by Sedgwick with regard to the whole 

 succession of life through geologic time, — that all belongs to one 

 great systema naturce. (Philos. Mag., iv. vol. viii. p. 359.) 

 fTo he continued in our next Number.) 



YI. — Eeview of the Contributions to Fossil Botany publtshed 

 IN Britain in 1872. 

 By William Carruthers, F.R.S. 

 The following papers have been published : — 



BiNNEY, E. W. On Stauropteris Oldhatnia, sp. nov. Monthly Microsc. Joum., 

 vol. vii., March, 1872, pp. 132, 133. 

 This name is proposed for a fossil from Oldham resembling Psaronius Zeidleri, 

 Corda ; the author records the discovery of specimens of Zygoptei'is, and his con- 

 viction that Cotta's Medullosa elegans is "merely the rachis of a fern, or a plant 

 allied to one." 



^ The Loiigmynd rocks in Shropshire are alone estimated at 20,000 feet; hut their 

 supposed equivalents, the Harlech rocks of Pembrokeshire, have a measured tliickness 

 of 3,300, while the Llanberris and Harlech rocks together, in North Wales, equal 

 from 4,000 to 7,000 feet, and the Lingula-flags and Tremadoc slates, united, about 

 7,000 feet. The Bala group in the Berwyns exceeds 12,000 feet, and the proper 

 Silurian, from the base of the Upper l>landovery or Mny Hill Sandstone, attiius from 

 5,000 to 6,000 feet; so that tlie aggregate of 30,000 feet may be considered below 

 the tiuth. [Mem. Geol. Survey, vol. iii. part 2, pp. 72, 222, and Sil,uria, 4th ed. 

 p. 185.] 



