part 4] JXJKASsic chkonology. 379 



gives a sketch of other Jurassic strata, the sequence o£ which 

 should be of some importance in connexion with the chronology of 

 the Oolite rocks. 



About three-quarters of a mile east of Thorncombe Beacon ^ 

 is Eypesmouth, a break in the cliffs where the little stream, the 

 Ejpe (pronounced ' Eep,' to rhyme with sheep) runs into the sea. 

 East of Eypesmouth is a lofty cliff of about a mile extending to 

 West Bay — the harbour of Bridport. 



The cliff is interesting geologically for three considerable faults : 

 one, seen best about a quarter of a mile east of Eypesmouth is 

 a fault of about 500 feet, bringing down Forest-Marble Beds to 

 about the level of Yeovilian strata {Diomortieria hemera) ; another, 

 about the same distance west of West Bay, brings down beds of 

 Fullei's'' Earth almost vertically — it is a fault of about 120 feet ; 

 the third, immediately west of West Bay, shows Yeovilian strata 

 of Dumortieria hemera or later — they are later than those on the 

 west oi the cliff — lying level with lower beds of Fuller's Earth : 

 a drop as regards the latter of about 150 feet. So the middle 

 and main portion of the cliff is let down by these faults. (See 

 diagram 1, sketch-elevation of Watton Cliff, p. 383.) 



The cliff faces about south-west by south and the faults run 

 approximately west and east. The effect of the westerly fault is 

 that destruction of the cliff has been hastened — there is a con- 

 siderable recess from Eypesmouth to where the fault is now most 

 visible, the cliff having been cleared back roughly along the line 

 of fault, except for some more or less tumbled strata at its foot. 

 The line of fault can be traced from what may be called ' the fault- 

 corner ' more or less towards Eypesmouth, where it disappears 

 beneath the sand and shingle of the shore. This fault is shown on 

 the 1-inch Greological Survey map. Sheet XYII, extending inland 

 some 8 miles to the foot of the Chalk Downs — the Dorset 

 Heights — near Long Bredy. It and the other faults run approxi- 

 mately parallel to, and are no doubt part of, the system of the 

 Weymouth Anticline. A ground-plan of the cliff and the faults 

 is appended (diagram 2, p. 384). 



In the autumn of 1916 a large block lying on the platform of 

 the fault-corner attracted my attention.''^ A portion that had 

 been broken off exposed a weathered surface with Thecidellcdy 

 and in some marl connected with them were unfamiliar ammonites 

 in a fragmentary condition — Hildoeeratids presenting almost the 

 appearance of those which characterize the f/^sc^Yes-beds of the 

 Inferior Oolite. Further search showed specimens of Tetra- 

 rhynchla tliomcombiensis, nom. nov.,^ evidently derived. 



Here was a case for investigation. The rock from which this 

 block had fallen was subsequently located high up in the cliff -face, 

 with also other tumbled blocks lying on a higher platform. Work 



1 I, 5, p. 59. 



- This block has disappeared, buried perhaps by a slide of clay. 



•^ See later, Paleeontological Note, p. 435. 



Q. J. G-. S. No. 312. 2 d 



