~ r

Vo]. L x x x . N o . 3 1 7 . PART 1,

T:IE

QUARTERLY JOURNAL

OF THE

GEOLOGICAL SOCIEIY.

EDITED BY

THE PERMANENT SECRETARY.

M,(RcH I7th, 192-k

[With Eight Plates, illustrating Papers by Dr. S. H. Haughton, Dr. H. Bolton, Dr. C. E. Tilley, Mr. J. E. ~. ~ r ~ , and Prof. S. H. Reynolds.]

LONDON :

LONGMANS, GREEN, AND CO.

P A ~ I S '--CHARL]E8 K I A N C K S I E C K , II RUE D E L I L L E .

SOLD AL~O AT T H E A P A R T ~ E N T ~ OF T H E SOCIETY.

Price Seven Shilbng~ and Sixperwe.

LIST OF TIIE OFFICERS AND COUNCIL OF TI lE

GE()LOGICAL SOCIETY OF LONDON. Elected February 15th, 1924.

~r~i~nt . John William Evans, C.B.E., D.Sc., LL.B., F.R.S.

~ict--~t't~i~nt~. Charles William Andrews, B.A., D.Sc., Prof. Albert Charles Seward, Sc.D.,

F.R.S. F.R.S., F.L.S. John Smith Flett, O.B.E., M.A., LL.D., Prof. William Whitehead Watts, LL.D.,

D.Sc., M.B., F.R.S. Sc.D., M.Sc., F.R.S.

~er~tarie~. Walter Campbell Smith, M.C., ~/I.A. ] James Archibald Douglas, lYI.A., D.Sc.

;fforeign t@~r~tarl). ~r~a~urer. SirArehibald Geikie, O.M., K.C,B., D.C.L., ] Robert Stansfield Herries, M.A.

LL.D., Se.D., F.R.S.

Charles William Andrews, P.A., D.Sc., P rof Herbert Leader Hawkins, D.Sc. F.R.S.

Frederick Noel Ashcroft, 1V[.A., F.C.S. Prof. Percy George Hamnall Boswell.

O.B.E., D.Se. Prof. Arthur Huber t Cox, D.Sc., Ph.D. Henry Dewey. Jame~ Archibald Douglas, M.A., D.Sc. Gertrude Lilian Elles, M.B.E., D.Se. John William Evans, C.B.E., D.Sc., LL.B.

F.R.S. John Smith Flett~ O.B.E., M.A., LL.D.,

D.Sc., M.B .F .R .S . Sir Archibald Geikie, O.M., K.C.B., D.C.L.,

LL.D Sc D., F.R.S. Frederick Henry Hatch, O.B.E., Ph.D.

Robert Stansfield Herries, ]VLA. Sir Thomas Henry Holland, K.C.S.I.,

K.C.I.E., D.Se., F.R.S. William Dickson Lang, M.A., Sc.D. Tressilian Charles Nicholas, M.A. Prof. Sidney Hugh Reynolds, M.A., Sc.D. Prof. Albert Charles Seward, Se.D.,

F.R.S., F.L.S. Walter Campbell Smith, ]VI.C., I~.A. Leonard James Spencer, IV[.A., Sc.D. Sir Aubrey Strahan, K.B.E., Sc.D., LL.D.,

F.R.S. Prof. William Whitehead Watts , LL.D.,

Sc.D., M.Se., F.R.S. Henry Woods, ~¢I.A., F.R.S.

~ e r m a n ~ n t ~¢cr~ tayp . L. L. Belinfante, lYI.Se.

~ibrarian. Arthur Greig.

STANDING PUBLIC~TIOIV COMMITTEE. Dr. J. W. Evans, President.

1V[r. W. Campbell Smith. ~ Secretaries. Mr. 1~. S. Herries, Treasurer. Dr. J. A. Douglas. J Dr. C. W. Andrews. Dr. W. D. Lang. Sir Aubrey Strahan. Dr. F. A. Bather. Mr. T. C. Nicholas. Prof. W. W. Watts . Prof. P. G. H. Boswell. Prof. S. H. Reynolds. 1Ylr. H. Woods. Dr. J. S. Flett. Dr. L. J . Spencer.

O R D I N A R Y M E E T I N G S O F T H E G E O L O G I C A L S O C I E T Y TO BE HELD AT BURLINGTON HOUSE.

SESSiO~ 1923-192~. 1924.

Wednesday, l~arch . . . . . . . . . . . . . . . . . . . . . . . . 26 ~ ,, April . . . . . . . . . . . . . . . . . . . . . . . . . . 9 ~ ,, May . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-- 21"

June . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - -25* The asterisks denote the dates on which the Council will meet.

JAMES SWIFT & SON L TM Makers of the Highest Grade

MICROSCOPES AND ACCESSORIES Contractors to al~ Scientific Dep~4rtmeJds of H.M. Goverr~me~L

ILLUSTRATED DESCRIPTIVE CATALO6UES OF

Petrological Microscopes giving specifications of various models,

AND

Petrological Accessories and I n s t r u m e n t s for Minera logy and Crystal- lography, including Re t rae tomete r s , Gonio-

meters , Record ing ~ l c r o m e t e r s , etc., w i l l b e s e n t p o s t f r e e o n r e q u e s t .

Univers i ty Opt ical Works 81 TOTTENHAM COURT ROAD, LONDON, W.I.

MICROSCOPES F O R

PETROLOGY Illustration shows Stand SY, having Synchronous Rotation

to the Nicols.

�9 "i . . . . . . . Catalo.que ~/7 _Pol post free

18

O G I L V Y & CO. (Bri t ish Agents for E. Leitz)

BLOOMSBURY SQUARE, LONDON, W.C.

CONTENTS.

Pages Proceedings of the Geological Society, Session 1923 24, inclading the Pro-

ceedings at the Annual General Meeting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....... i- x]v

PAPEI~S READ, Page

J 1. Dr. S. H. Hau%hton on Reptilian Remains from the Karroo Beds of East Africa (Plates I & II) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-

2. Prof. L. Dollo & Dr. P. Teilhard de Chardin on the Paleocene Mammalia of d Belgium [in French~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

j 3. Dr. H. Bolton on Drybroo!Aa cu, bitalis from the Coal Measures of the Forest of Dean (Plate III) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

~/ 4. Dr. C. E. Tilley on Contact-Metamorphism in the Comrie Area of the Perth- shire Highlands (Plate IV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

~] 5. Mr. J. F. N. Green on the Structure of the Bowmore-Portaskaig District of Islay (Plates V & VI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

¢t 6. Prof. S. H. Reynolds on the Igneous Rocks of. the Tortworth Inlier (Plates VII & VHI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . . . . 106

[The Editor of the Quarterly Journal is directed t0 make it known to the Public that ~he A u t h o r s a l o n e a r e r e s p o n s i b l e fo r t h e f a c t s a n d o p i n i o n s c o n t a i n e d in t h e i r r e s p e c t i v e P a p e r s , a n d fo r ~he c o r r e c t n e s s of t h e i r r e f e r e n c e s . ]

A u t h o r s d e s i r o u s of c o m m u n i c a t i n g p a p e r s to t h e S o c i e t y w i l l be s u p p l i e d , on a p p l i c a t i o n to t h e S e c r e t a r y , w i t h a c o p y of ' I n s t r u c t i o n s to A u t h o r s ' , i s s u e d by t h e C o u n c i l on ~he r e c o m - m e n d a t i o n of t h e P u b l i c a t i o n C o m m i t t e e .

The Library at the Apartments of the Society is open every Week Day from Ten o'clock until Five, except on Saturdays (when the hours are from 10 to 1), a n d e x c e p t d u r i n g t h e f o r t n i g h t c o m m e n c i n g on t h e f i r s t M o n d a y in S e p t e m b e r , when the Library is closed for the purpose of cleaning.

Vol . L X X X . N O . S 1 8 . Px~T 2.

THE

QUARTERLY JOURNAL

OF THE

GEOLOGICAL SOCIETY.

EDITED BY

THE PERMANENT SECRETARY.

JULY 25th, 1924.

[With Sixteen Plates, illustrating Papers by Dr. K. S. Sandford, Prof. E. J. Garwood a Miss E. Goodyear, Dr. L. J. Wills,

and Mr. C. W. 0sman.]

LONDON :

LONGMANS, GREEN, AND CO.

PARIS:--CHARLES KLINCKSIECK, 1[ RUE DE LILLE.

$OLD ALSO AT THE APARTI~ENTS OF THE SOCIETY.

Price Seven Shillings and Sixpence.

LIST OF THE OFFICERS AND COUNCIL OF THE

GEOLOGICAL SOCIETY OF LONDON. Elected February 15th, 1924.

Pr~i~mt. John William Evans, C.B.E., D.Sc., LL.B., F.R.S.

~ic~--~r~i~nt~. John Smith Flett, O.B.E., M.A, LL.D., Prof. William Whitehead Watts, LL.D.,

D.Sc., M.B., F.R.S. Sc.D., M.Se., F.R.S. Prof. Albert Charles Seward, Sc.D,,

F.R.S., F.L.S. ~cr~tari~.

Walter Campbell Smith, M.C., M.A. James Archibald Douglas, M.A., D.Sc.

~ortigrt btcr~tar~. ~r~a~ur~r. SirArchibald Goikie, 0.M., K.C.B., D.C.L., Robert Stansfield Herries, M.A.

LL.D., Sc.D, F.R.S. C@~N©aL.

Frederick Noel Asheroft, M.A., F.C.S. Prof. Percy George Hamnall Boswell

O.B.E., D.Se. Prof. Arthur Hubert Cox, D.Sc., Ph.D. Henry Dewey. James Archibald Douglas, M.A., D.Sc. Gertrude Lilian Elles, M.B.E., D.Sc. John William Evans, C.B.E., D.Sc., LL.B.

F.R.S. John Smith Flett, O.B.E., M.A., LL.D.,

D.Se., M.B., F.R.S. Sir ArChibald Geikie, O.M., K.C.B., D.C.L.,

LL.D., Sc.D., F.R.S. Frederick Henry Hatch, O.B.E., Ph.D. Prof. Herbert Leader Hawkins, D.Sc.

RobertStansfield Herries, I~I.A. Sir Thomas Henry Holland, K.C.S.I.,

K.C.I.E., D.Sc., F.R.S. William Dickson Lang, M.A., Sc.D. Tressilian Charles Nicholas, O.B.E., M.A. Prof. Sidney Hugh Reynolds, M.A., Sc.D. Prof. Albert Charles Seward, Sc.D.,

F.R.S., F.L.S. Walter Campbell Smith, M.C., ~/I.A. Leonard James Spencer, i%I.A., Sc.D. Sir Aubrey Strahan, K.B.E., Sc.D., LL.D.,

F.R.S. Prof, William Whitehead Watts, LL.D.,

Sc.D., M.Sc., F.R.S. Henry Woods, M.A., F.R.S.

~trman,nt ,~,crttal'y. L. L. Belinfante, M.Sc.

~Librarian. Arthur Greig.

S T A N D I N G PUBLICATIOt~ COMMITTEE. Dr. J. W. Evans, President.

Mr.Dr. J.W'A.CampbellDouglas.Smith" t Secretaries. Mr. R. S. Herries, Treasurer.

Dr. F. A. Bather. Mr. T. C. Nicholas. Sir Aubrey Strahan. Prof. P. G. H. Boswell. Prof. S. H. Reynolds. Prof. W. W. Watts. Dr. J. S. Flett. Dr. L. J. Spencer. Mr. H. Woods. Dr. W. D. Lang.

O R D I N A R Y M E E T I N G S O F T H E G E O L O G I C A L S O C I E T I ' TO BE HELD AT BURLINGTON HOUSE.

SESSION 1924-1925. 1924.

Wednesday, November ..................... 5v--19 v December ...................... 3 --17~

1925. Wednesday, January ... . . . . . . . . . . . . . . . . . . . . . 7~--21 *

,, February (Anniversary Meeting, Friday, February 20th). 4*--25 ~

,, March ... . . . . . . . . . . . . . . . . . . . . . 1 1 - - 2 5 ~ ,, April : . . . . . . . . . . . . . . . . . . . . . . . . . . 22 ~ ,, May . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 -- 20 ~ ,, June ... . . . . . . . . . . . . . . . . . . . . . ... 10"--24

The asterisks denote the dates on which the Council will mee~.

JAMES SWIFT SON L TO' M a k e r s of t h e Highest G r a d e

MICROSCOPES AND ACCESSORIES Contractors to a[~ Scientific Departments of H.M. Government.

Petrological Microscopes " P r i m e x , " " A d v a n c e d S t u d e n t , " " P e t r o s , " " S u r v e y " a n d " D i c k " Mode l s fo r al l c l a s se s o f P e t r o l o g i c a l a n d M i n e r a l o g i c a l R e s e a r c h .

Petrological Accessories a n d I n s t r u m e n t s fo r M i n e r a l o g y a n d C r y s t a l - l o g r a p h y , i n c l u d i n g R e f r a c t o m e t e r s , G e n i e -

m e t e r s , R e c o r d i n ~ M i c r o m e t e r s , e tc .

Illustrated Descriptive Catalogues on request.

"Advanced Student"

University Optical Works 81 TOTTENHAM COURT ROAD, LONDON, W.I.

M I C R O . O B J E C T I V E S SELECTED FOR P E T R O L O G Y

A~ s . d . No. 1 (I~") 0"IlN.A. 1 6 6

2 (1") 0"21 ,, 1 6 6 3 ( i") 0.25 ,, 1 6 6 3 a ( ~ " ) 0 % 0 , , 1 15 0 4 ,v J 0'40 ,, 2 4 0 5 Q " ) 0"64 ,, 2 4 0 6 Q") 0.85 ,, 2 12 6 7 (~") 0'85 ,, 2 12 6

Catalogue (47 Pol) post fi'ee, .qivin.q f id l particulars of JIicroscopes, Objectives, ~yepieces , Accessories.

O G I L V u & CO. ( B r i t i s h A g e n t s fo r ]iL Lei tz)

18 BLOOMSBURY SQUARE, LONDON, W.C.I.

CONTENTS.

Pages Proceedings of the Geological Society, Session 1923-24, including the Presi-

dent's Anniversary Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xlvii-civ

¢ PAPERS READ.

Page 7. Dr. K. S. Sandford on the River-Gravels of the Oxford District

(Plate IX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

t ] 8. Dr. F. S. Wallis on the Avonian of the Tytherington-Tortworth Wickwar Ridge (Abstract) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

t/ 9. Miss A. E. Bamber on the Avonian of the Western Mendips, from the Cheddar Valley Railway to the Sea, west of Brean Down (Abstract) ...... 182

10. Prof. E. J. Garwood & Miss E. Goodyear on the Lower Carboniferous ~/ Succession in the Settle District (Plates X-XXI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

11. Dr. L. J. Wills on the Development of the Severn Valley in the Neighbour- ~/ hood of Iron-Bridge and Bridgnorth (Plates XXII & XXIII) . . . . . . . . . . . . . . . 274

12. Mr. C. W. Osman on the Geology of the Northern Border of Dartmoor J (Plate XXIV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315

[The Editor of the Quarterly Journal is directed to make it known to the Public tha t t h e A u t h o r s a l o n e a r e r e s p o n s i b l e fo r t h e f a c t s a n d o p i n i o n s c o n t a i n e d in t h e i r r e s p e c t l v e P a p e r s , a n d f o r t h e c o r r e c t n e s s of

t h e i r r e f e r e n c e s . ]

A u t h o r s d e s i r o u s of c o m m u n i c a t i n g p a p e r s to t h e S o c i e t y w i l l be s u p p l i e d , on a p p l i c a t i o n to t h e S e c r e t a r y , w i t h a c o p y of , I n s t r u c t i o n s to A u t h o r s ' , i s s u e d by t h e C o u n c i l on t h e r e c o m - m e n d a t i o n of t h e P u b l i c a t i o n C o m m i t t e e .

The Library at the Apartments of the Society is open every Week Day from Ten o'olook until Five, except on Saturdays (when the hours are from 10 to 1), a n d e x c e p t d u r i n g t h e f o r t n i g h t c o m m e n c i n g on t h e f i r s t M o n d a y in S e p t e m b e r , when the Library is closed for the purpose of cleaning.

V o l . L X X X . PA~T 3.

N o . 3 1 9 .

T I ~

QUARTERLY

OF THE

GEOLOGICAL

JOURNAL

SOCIETY.

EDITED BT

THE PERMANENT SECRETARY.

OCTOBER 4th, 1924.

[With Fifteen Plates, illustrating Papers by Prof. W. S. Boulton, Mr. D. J. Farquharson, Mr. H. P. Lewis, Mrs. J. Lo~gstaff, and Prof. S. H. Reynolds & Dr. E. Greenly.]

LONDON :

LONGMANS, GREEN, AND C0.

PARIS : - -CHARLE8 KLINCKSII~CK, I1 RUE DE LILLE.

SOLD ALSO AT THE APARTI~IENT~ OF THE SOCIETY.

.Price Seven Shillings and Sixpence.

LIST OF THE OFFICERS AND COUNCIL OF THE

GE()LOGICAL SOCIETY OF LONDON. Eleete~ r~ei,~y~;£~, 1924

John William Evans, C.B.E., D.Sc., LL.B., F.R.S.

~ic~--~r~i~tnt~. John Smith Flett, O.B.E, M.A., LL.D., Prof. William Whitehead Watts , LL.D.,

D.Sc., M.B., F.lg.S. Sc.D., M.Sc., F.R.S. Prof. Albert Charles Seward, Sc.D.,

F.R.S., F.L.S. ~cr~tat 'i~.

Walter Campbell Smith, 1~¢I.C., ~ .A. I James Archibald Douglas, M.A., D.Se.

~ortiga btcr~tar~. ~r~a~urtr. SirArehibald Geikie, O.M., K.C.B., D.C.L., Robert Stansfield Herries, M.A.

LL.D., So.D., F.R.S.

Frederick Noel Ashcroft, M.A., F.C.S. Prof. Percy George Hamnall Boswell

O.B.E., D.Sc. Prof. Arthur Huber t Cox, D.Sc., Ph.D. Henry Dewey. James Archibald Douglas, !~I.A., D.Sc. Gertrude Lilian Elles, M.B.E., D.Sc, John William Evans, C.B.E., D.Se., LL.B.

F.R.S. John Smith Flett , O.B.E., l~.A., LL.D.,

D.Sc., M.B., F,Ig.S. Sir Archibald Geikie, O.lV[., K.C.B.,D.C.L.,

LL.D., Se.D, F,R.S. Frederick Henry Hatch, O.B.E., Ph.D. Prof. Herbert Leader Hawkins, D.Se.

Robert Stansfield Herries, M.A. Sir Thomas Henry Holland, K.C.S.I., • K.C.I.E., D.Sc., F.R.S. William Dickson Lang,/VLA., Sc.D. Tressilian Charles Nicholas, O.B.E., M.A. Prof. Sidney Hugh Reynolds, M.A., Sc.D. Prof. Albert Charles Seward, Sc.D.,

F.R.S., F.L.S. Walter Campbell Smith, lW.C., I~I.A. Leonard James Spencer, lVLA., Se.D. Sir Aubrey Strahan, K.B.E., Sc.D., LL.D.,

F.l%.S. Prof. William Whitehead Watts , LL.D.,

Sc.D., M.Sc., F.R.S. Henry Woods, M.A., F.R.S.

Btrmanent Dtcrttar~. L. L. Belinfante, lVLSc.

~ibrarian. Arthur Oreig.

STANDING PUBLICATION COMMITTEE. Dr. J. W. Evans, President.

Mr. W. Campbell Smith. ] Dr. J. A. Douglas. f Secretaries. Mr. R. S. Herries, Treasurer.

Dr. F. A. Bather. Mr. T. C. Nicholas. Sir Aubrey Strahan. Prof. P. G. H. BoSwell. Prof. S. H. l~eynolds. Prof. W. W. Wat ts . Dr . J. S. Flett. Dr. L. J. Spencer. Mr. H. Woods. Dr. W. D. Lang.

O R D I N A R Y M E E T I N G S O F T H E G E O L O G I C A L S O C I ~ . T ~ TO BE HELD AT BURLINGTON HOUSE.

S~ssio~¢ 1924-1925. 1924.

Wednesday, November . . . . . . . . . . . . . . . . . . . . . 5v--19 v December .. . . . . . . . . . . . . . . . . . . . 3 - -17 ~

1925. Wednesday, January . . . . . . . . . . . . . . . . . . . . . . . . 7v--21 ~

,, February (Anniversary Meeting, Friday, F~bruary 20th). 4~--25 ~

,, March . . . . . . . . . . . . . . . . . . . . . . . . 1 1 - - 2 5 ~ ,, April . . . . . . . . . . . . . . . . . . . . . . . . . . 22 ~ ,, May . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 -- 20 ~

June . . . . . . . . . . . . . . . . . . . . . . . . . . . 10~--24 The asterisks denote the dates on which the Council will meet.

JAMES SWIFT & SON L TD. M a k e r s o f t h e H i g h e s t G r a d e

MICROSCOPES AND ACCESSORIES Contractors to a~t Scientific Departments of H.M. Government.

J U S T P U]~LISH.ED

NEW C A T A L O G U E OF

P E T R O L O G I C A L M I C R O S C O P E S

P o s t f r e e o n r e q u e s t

Univers i ty Optical Works

81 T O T T E N H A M C O U R T ROAD, LONDON.

eL tz FOLDING POCKET MAGNIFIERS

C o m p o s e d o f t h r e e c e m e n t e d l e n s e s t o t h e S t e i n h e i l f o r m u l a , t h e y f u r n i s h a l a r g e , f i a t a n d c o l o u r l e s s i m a g e . I n t h e f o l l o w i n g p o w e r s : • 6, 8, 10, 12, 16, 20, 30 a n d 40. I n l e a t h e r p o u c h e s , P.ls. e a c h .

Catalo//ue, 47C, ?ost free.

PETROLOGICAL MICROSCOPES FOR ALL CLASSES OF WORK

Catalogue, 47t)ol, post free.

O G I L V Y & CO. (British Agents for E. Leitz)

18 BLOOMSBURY SQUARE, LONDON, W.C.I.

CONTENTS.

PAPERS READ. Page

13. Sir Arthur Smith Woodward on Tr is tych ius arcu~tus . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

t / 14. Prof. W. S. Boult~n on the Breccla-Bed underlying Nechells (Plate XXV). 343

. / 15. Mr. D. J. Farquharson on the Geology of Southern Gaernsey (Plate XXVI) 374

• / 16. Mr. H. P. Lewis on Upper Vis~an Corals of the Genu~ C a n i n i a (Plates

XXVII-XXX) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389

j 17. Mrs. J. Longstaff on Ordovician and Lower Silurian Gasteropoda from

Girvan (Plates XXXI-XXXVIII) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408

j 18. Prof. S. H. Reynolds & Dr. E. Greenlyon the Geological Structure of the

• Clev~don-l~ortishead Area, Somerset (Plate XXXIX) .. . . . . . . . . . . . . . . . . . . . . . . . 447

[The Edifier of the Quarterly Journal is directed to make it known to the Public that t h e A u t h o r s a l o n e a r e r e s p o n s i b l e f o r t h e f a c t s a n d o p i n i o n s e o n t a i l l e d in t h e i r r e s p e c t i v e P a p e r s , a n d t~or t h e c o r r e c t n e s s of t h e i r r e f e r e n c e s , ]

A u t h o r s d e s i r o u s ~ of c o m m u n i c a t i n g p a p e r s t o t h e S o c i e t y w i l l be s u p p l i e d , on a p p l i c a t i o n t o t h e S e c r e t a r y , w i t h a Copy of ' I n s t r u c t i o n s to A u t h o r s ' , i s s u e d b y t h e C o u n c i l on t h e r e c o m - m e n d a t i o n of t h e P u b l i c a t i o n C o m m i t t e e .

The Library at the Apartments of t h e Society is open every Week Day fr~m Ten o'clock until Five, except on Saturdays (when the hours are from 10 to 1), a n d e x c e p t d u r i n g t h e f o r t n i g h t c o m m e n c i n g on t h e f i r s t M o n d a y in S e p t e m b e r , when the Library is closed fo r the purpose of cleatling.

Vol. L X X X . N o . 3 a O . PA~T 4.

T H E

Q U A R T E RLY J O U R N A I~

OF THE

GEOLOGICAI, SOCIETY.

J D I T E D B Y

THE PERMANENT SECRETARY.

I)ECEM13ER 31st, 192~.

[With Six Plates, illustrating Papers by Dr. H. H. Thomas & Prof. A. H. Cox, 1Kr. L. Hawkes, and Profi 0. T. Jones.]

LONDON :

L O N C ~ M A N S , G R E E N , A N D CO.

I~ARIS:--CHARLE8 KLINCKSlECK, l l RU~, DE LILLE.

SOLD ALSO AT THE APART3s OF THE SOCIETY.

Price Seven Shillings and Sixpence.

L I S T OF T t t E O F F I C E R S AND C O U N C I L OF T H E

GE()LOGICAL SOCIETY ()F L()ND()N. Eloeted i~br~iy 5 ~ , ~ 9.o~.

John William Evans, C.B.E., D.Sc., LL.B., F.R.S. "

John Smith Flett, O.B.E., M.A., LL .D , Prof. William Whitehead Watts , LL.D., D.Sc, M.B., F.R.S. So.D, M.Sc.. F.R.S.

Prof. Albert Charles Seward, Sc.D..Sir Arthur Smith Woodward, LL.D., F.R.S., F.L.S. " F.R.S., F.L.S.

~c~'~tat'i~. V~'e]+.er Campbell Smith, M.O., ~I.A. I James Archibald Douglasi :~I.A., D.Sc.

~or~ign ~crctarp. E r~a~ur~r. [Vacant.] I Rober~ Stansfield Herries, M.A.

Frederick Noel Asheroft, ~LA., F.C.S. Prof. Percy George Hamnall Boswell.

O.B.E., D.Sc. Prof. Arthm" Huber t Cox, D.Se., Ph.D. Henry Dewey. James Archibald Douglas, I~I.A., D.Sc. Gertrude Lilian Elles, !~I,B.E., D.Se. John William Evans, C.B.E., D.Sc., LL.B

F.R.S. John Smith Flett, O.B.E., ]~.A., LL.D.,

D.Sc., M.B., F.R.S. Frederick Henry Hatch, O.B.E., Ph.D. Prof. Herbert Leader Hawkins, D.Se. I~obert Stansfield Herries, ]V[.A. Sir Thomas Henry Holland, K.C.S.I.,

K.C.I.E., D.Sc., F.R.S.

~}erman~nt ~creta~'~). L. L. Belinfante, M.Sc.

Y.ft~rarian. Arthur Greig.

S T A N D I N G P U B L I C A T I O N COMMITTEE. Dr. J. W. Evans, PresidenL

]~Ir. W. Campbell Smith. ~ Secretaries. Dr. J. A. Douglas. J

Dr. F. A. Bather. Mr. T. C. Nicholas. Prof. P. G. H. Boswell. Prof. S. H. Reynolds. Dr. J. S. Flett. Dr. L. J. Spencer. Dr. W. D. Lang.

William Dickson Lang, M.A., Sc.D. Tressilian Charles Nicholas, O.B.E.,

M.A. Prof. Sidney Hugh Reynolds, 1VI.A.,

Sc.D. Prof. Albert Charles Seward, Sc .D. ,

F.R.S., F.L.S. Walter Campbell Smith, M.C., M.A. Leonard James Spencer, ~VI.A., Sc.D. Sir Aubrey S~rahan, K.B.E., Se.D., LL.D.,

F.R.S. Prof. William Whitehead Watts , LL.D.,

Sc.D., M.Sc., F.R.S. Henry Woods, M.A., F.R.S. Sir Arthur Smith Woodward, LL.D.,

FR.S., F.L.S.

Mr. R. S. Herries, Treasurer.

Sir Aubrey Strahan. Prof. W. W. Watts . Mr. H. Woods.

O R D I N A R Y M E E T I N G S O F T I l E G E O L O G I C A L S O C I E T Y TO BE H E L D AT BURLINGTON HOUSE.

S~ssIoN 1 9 2 4 - 1 9 2 5 . 1925.

Wednesday, January . . . . . . . . . . . . . . . . . . . . . . . . 7~--21 * ,, February (AnniversaryMeeting,

Friday, February 20th). 4~--25 * ,, l~Iarch . . . . . . . . . . . . . . . . . . . . . . . . 1 1 - - 2 5 v ,, April ....... . . . . . . . . . . . . . . . . . . . 22 ~ ,, May . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 -- 20 ~

June ..... . . . . . . . . . . . . . . . . . . . . . . 10~---24 The asterisks denote the dates on which the Council will meet.

MIGROSGOPES F O R

PETROLOGY

Illustration shows Stand SY, having Synchronous Rotation to the Nicols.

Catalo.q,ee 47 _Pol .post fi'ee

O G I L V Y & CO. (Brit ish Agents for E. Leitz)

20 MORTIMER STREET, LONDON, W.I.

JAMES SWIFT & SON L TD. M a k e r s o f t h e H i g h e s t G r a d e

MICROSCOPES AND ACCESSORIES Contr(~ctors to al~ Scie~dific Departments of H.M. Govern mel~.

Petrological Microscopes " P r i m e x , " " A d v a n c e d Student," " P e t r o s , " ~' Survey" and '" Dick" ~, odels for all classes of Petrological and Minera 'og ica l Resea rch .

Petrological Accessories a n d I n s t r u m e n t s for Minera logy and Crystal- lography, including Ref rac tomete r s , G o n i o -

meters , Record ing l~ ierometers , etc.

_Tllw~trate.l Dsseripr C~alo.~a~s o~ roqaes& " Advsneed Student"

Univers i ty Optical W o r k s 81 T O T T E N H A M COURT ROAD, LONDON.

C 0 N T E N T S.

PAPERS READ. Page

19. Mr. W. B. Wright on tile Age and Origin of the Lough Neagh Clays ...... 468

20. Dr. A. Heard & Mr. R. Davies on the Old Red Sandstone of l~he Cardiff

District . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489

21. Dr. H. H. Thomas & Prof. A. H. Cox on the Volcanic Series of Trefgarn, Roch, & Ambleston, Pembrokeshire (Plate XL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520

22. Mr. L. Hawkes on an Olivine-Dacite in tile Tertiary Volcanic Series of Eastern Iceland (Plates XLI & XLII) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549

23. Prof.'O. T. Jones on the Upper Towy Drainage-System (Plates XLI I I - XLV) .................................................................................... 568

[TITLE-PAGE, CONTENTS, and INDEX to Vo]. LXXX.]

[The Editor of the Quarterly Journal is directed to make it known to the Public that t h e A u t h o r s a l o n e a r e r e s p o n s i b l e fo r t h e f a c t s a n d o p i n i o n s c o n t a i n e d in t h e i r r e s p e c t i v e P a p e r s , a n d fo r t h e c o r r e c t n e s s of

t h e i r r e f e r e n c e s . ]

A u t h o r s ' d e s i r o u s of c o m m u n i c a t i n g p a p e r s to t h e S o c i e t y w i l l be s u p p l i e d , on a p p l i c a t i o n to t h e S e c r e t a r y , w i t h a c o p y of ' I n s t r u c t i o n s to A u t h o r s ' , i s s u e d by t h e C o u n c i l on t h e r e c o m - m e n d a t i o n of t h e P u b l i c a t i o n C o m m i t t e e .

The Library at the Apartments of the Society is open every Week Day from Ten o'clock until Five, except on Saturdays (when the hours are from 10 to 1), and except during the fortnight commencing on the first Monday in September, when the Library is closed for the purpose of cleaning.