SECTIONAL TRANSACTIONS.— C. 331 



These air-pore groups appear to be segregated in depressed polygonal areas which 

 occur over the whole of the upper surface of the plant. 



The inner cells of the thallus, which do not underlie the polygonal areas, consist 

 of fairly uniform collenchyma ; below the air-pores the cells appear to consist of 

 irregularly sized thin-waUed parenchymatous cells associated with large air-spaces. 



Spirally thickened elements have been observed in several ' treated ' fragments, 

 but their exact position in* the thallus has not yet been determined. 



The ventral layer has not yet yielded much information of morphological interest. 

 Intertwining filaments recovered from below the lower surface are interpreted as 

 rhizoids. 



In several features, Eohepatica dyfriensis bears some general resemblances to 

 Marchantia. 



Prof. H. Gr. A. HiCKLiNG. — The Geological Structure of the English Pennines. 



A contoured map of the post-Coal Measure folding of the Carboniferous rocks in 

 the Pennines and adjoining coalfields was produced by taking the existing levels of 

 various Carboniferous strata throughout the area, and reducing them to the common 

 datum of the Barnsley coal-seam of Yorks and Notts, the Trencherbone of Lancashire, 

 Banbury 7-feet of North Staffs and Hutton or Low Main of Northumberland and 

 Durham, which have been chosen as approximately corresponding horizons. The 

 central area of the northern Pennines was contoured on the Great or Main Limestone, 

 which can be traced throughout nearly the whole area. 



The general character of the folding thus represented strikingly confirms the 

 distinctness of the northern and southern Pennines, and shows the break at the 

 Craven faults to be even more important than has been usually supposed. The area 

 south of the break is somewhat strongly folded about an irregular dome which is 

 elongated N.N.W.-S.S.E. This is flanked on the east by the synclines of the Yorks 

 and Notts coalfields whose axes trend N.W.-S.E. (i.e. ' Charnian '), while to the west 

 the folding is much stronger and its dominant lines clearly N.E.-S.W., or 'Cale- 

 donian.' The ' Caledonian ' folding attains its climax in the many strong echeloned 

 anticlines which lie between the Burnley Coalfields and the Craven faults, where it 

 abuts sharply and discordantly against the almost unfolded northern Pennines or 

 ' Rigid block.' 



The northern ' Rigid block,' extending from the Craven faults to the Tyne, shows 

 moderately strong transverse folding in the Stainmore gap and the Tyne valley. The 

 former folds divide it into a southern ' Ingleborough ' block and Northern ' Cross 

 Fell block,' whUe the latter separates it from the more folded area of Northumberland. 

 The whole block shows evidence of a slight tilt towards the north-east at an early 

 date, extending from the Lake District to Durham, where it terminates in the 

 Sunderland syncline, a fold of definitely ' Charnian ' trend. 



Though the main folding of the Pennines is of Hercynian age, there is thus almost 

 no indication of Hercynian or Armorican trends in the folds produced, the lines of 

 movement being evidently influenced by older structures. Comparison of the 

 present slight easterly tilt of the Carboniferous of the northern Pennines with the 

 tilt of the Permian rocks shows them to be nearly the same, and demonstrates con- 

 clusively that no tectonic ridge can have existed in thi.s area in Mesozoic times. The 

 very intimate relation of this easterly tilt to the existing surface features suggests a 

 relatively modern movement, to which the ' Pennine Chain ' as a topographic feature 

 is mainly due. 



The Pennines afford a splendid example of the relation between earth-movement 

 and sedimentation in Carboniferous times. Over much of the northern Pennines 

 subsidence was small and consequently the whole thickness of Carboniferous 

 sediments deposited possibly never exceeded 3,000 feet. South of the Craven faults 

 subsidence exceeded 15,000 feet, resulting in an equal thickness of sediments. The 

 former area of small movement remains still unfolded, while the latter shows intense 

 folding. The warping of the base of the Carboniferous series which took place while 

 the remainder of those rocks were being deposited was approximately equal to all 

 the warping of the area which has taken place subsequently. 



Dr. A. Raistrick. — The Moraines of Western Durham. 



