Reports and Proceedings — Geological Society of London. 139' 



mosses ; the clays over tbis have probably been formed in a lake, 

 possibly clue to a beaver-dam. In the gravel-bed are found imple- 

 ments formed of flint quarried from the Chalk, or of quartzite from 

 pebbles of the Northern Drift, all remarkable for their size, beauty, 

 and freshness, together with the remains of large mammals, including 

 the mammoth. The old surface, from which the river-bed has been 

 eroded, has also yielded implements associated with quartzites, 

 quartz -pebbles, and lydianstone, gravel from the Thames Valley, 

 limestone pebbles, Oolitic fossils, and sand. Tins deposit is regarded 

 as remanie from the Northern Drift, probably laid down under the 

 action of ice, as shown by the flask-like shape of the pits, the vertical 

 position of some of the pebbles, and the jamming-in of masses of 

 sand, probably in a frozen condition. Further, the Oxford Clay 

 beneath the surface is weathered and shaken to a depth of 10 or 12 

 feet, except where cut off by the descending depth of the river-bed. 

 The implements are small, ordinary in shape, and made of flint, not 

 quarried, but mostly taken from the Drift, and they are much 

 weathered, stained, and patinated. The occurrence of an older set 

 of implements, differing so markedly from those of the river-drift, 

 leads the author to explain the peculiar implementiferous drift of 

 Iffley as containing implements of two kinds and two dates. Those 

 that are unweathered are contemporaneous with the deposit, and like 

 those of the Wolvercote river-bed ; while those that are stained with 

 ochre, or deeply patinated, have been derived, like the Oolitic fossils. 

 Tertiary conglomerate, quartzites, and volcanic rocks, from an older - 

 deposit. The author believes that the frequent occurrence of 

 weathered and unweathered implements in a single deposit may be 

 explained generally in this way ; and he further infers that the time 

 between the Drift and the river-bed was prolonged, and that the 

 interval may^have been as long as that which separates the epoch 

 of the river-bed from the present day, his evidence being simply the 

 patination of the flints. In conclusion the author suggests that there 

 are three classes of implement-bearing drifts, the ice-drifts being the 

 earliest and the river-drifts the latest, while the wash-drifts may 

 belong to more than one stage. 



2.— January 20th, 1904.— Sir Archibald Geikie, D.C.L., D.Sc, 

 Sec. K.S., Vice-President, in the Chair. 

 The Secretary announced that the Council had communicated the 

 following resolution of sympathy to Mrs. Etheridge : — 



"That the Council desire to place on record their great regret at the death of 

 Mr. Eobert Etheridge, P.R.S., formerly President of this Society, who did so much 

 during his long life to advance Geological Science and to promote the interests of 

 the Society." 



The following communications were read : — 



(1) "On the Jaws of Ptychodns from the Chalk." By Arthur 

 Smith Woodward, LL.D., F.R.S., F.L.S., F.G.S. 



Hitherto no traces of the cartilaginous jaws of this fish have been 

 found in association with the dentition ; but Mr. Henry Willett 



