Upper Ehjetic. { 



Lower EhjETic, 



or Zone of 

 Avicula contorta. 



82 Professor S. S. Jevons — Scratches on Minerals. 



Section at "Woodnorton, near Ea'^esham. 



{Limestone, bluish-grey ; Ostrea Uassica 

 Clay, yellowish, marly 

 Limestone, in two layers, bluish-grey, shelly ; Ostrea 

 Uassica, Modiola minima 

 '1. Shales, brown, thinly laminated 



2. Limestone, hard, bluish-black; Modiola minima 



3. Shales, grey and greenish-grey, laminated in 

 places, usually non-laminated, marly ... 5 4 



4. Limestone (£'s^/ima - bed) , creamy yellow, 

 argillaceous ; Estheriaminuta-f&x.Brodieana, 

 Naiadita lanceolata ... ... ... ... 3-5 



5a. Shales, grey, greenish-grey, and yellowish, \ 



thinly laminated in places, usually non- (14^ o 

 laminated, marly; shell fragments ... ... l 



f5b. Shales, dark-coloured / 



6. Limestone nodules, containing Schizodus Eivaldi ; 

 resting upon a laminated limestone fuU of 

 shell fragments ; Pecten valoniensis, Schizodus 

 Ewaldi, Protocardium, a.uA Pleurophorus ... 8 



7. Shales, black, laminated (visible) 6 



This section is the only one of the Upper Ehaetic stage in the 

 county, and accordingly is of considerable importance. At Wainlode 

 Cliff the Upper Eheetic is 13 feet 4 inches in thickness, here it is 

 about 19 feet 7 inches, i.e., deducting 3 feet from the thickness 

 of the lowest deposit of the upper stage, which would probably be 

 found to belong to the Avicula contorta zone or Lower Rhaatic had 

 it been possible to investigate it for fossils. 



Concerning the nature of the deposit above the beds exposed at 

 Crowle and below those seen at Woodnorton the section at Dun- 

 hampstead affords some assistance. These intervening beds at 

 Dunhampstead are as follows : — 



ft. ins. 



6. Limestone nodules 10^ 



7. Shales, black, clayey, pyritic (4 feet less 1 ft. 5 in.) 2 7^ 



8. Sandstone, brown, micaceous ; Modiola minima, Schizodus ... 3 



9. Shales, brown, clayey ... ... ... ... ... ... 1 2 



10. Sandstone, yellowish (weathering brown), micaceous ; Modiola 



minima, Schizodus, annelid -tracks, fish scales ... 5 



If this record be read with those made at Crowle and Woodnorton, 

 a generalised section will be had of the Ehastic series as it occurs 

 in Worcestershire, 



« 2 



VIII. — Scratches on Minerals in Thin Sections. 



By H. Stanley Jevons, M.A., F.G.S., Lecturer in Mineralogy and Demonstrator 

 in Geology in the IJniversity of Sydney. 



rpHERE is an exceedingly simple method of distinguishing biotite 

 X from brown hornblende in thin sections under the microscope, 

 which, so far as I am aware, has not yet been described. As it 

 may possibly be of assistance to beginners, I submit a brief 

 account thereof. 



Let any section of biotite which shows the cleavage and pleo- 

 chroism be turned between crossed nicols until the light is almost, but 



' On authority of Mr. "W. J. Harrison, F.G.S. : vide Proc. Dudley and Midland 

 Geol. See, vol. iii, No. 5 (1877), p. 121. 



