Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/811

Rh thick for its size. Mr. Keeping picked it up out of the debris, but did not notice having dug it out. I have myself little doubt about its belonging to the deposit. It is of a blackish hue, polished, with white porcellanous mottling, and has specks of botryoidal limestone adhering to it; all which characters mark many of the flint fragments in the silt.

The area excavated for the large collection was about 14 yards from north to south, by about 6 yards from east to west.

If we compare the above list of Mammalia with that given by Mr. Jukes-Browne for Barnwell, we find the following species common to Barrington and Barnwell:—

At Barnwell, but absent from Barrington, Equus fossilis.

It is observable that a small undetermined Cervus is mentioned also at Barnwell.

It will be seen, then, that the Mammalia belong to the same group at these two localities. We have, however, at Barrington neither of the distinctive shells Cyrena fluminalis and Unio litoralis. The absence of either, or both, of these might be accidental; for it is only in places, even at Barnwell, that they are found; but I think the greater distance from the sea would be sufficient to account for the absence of the Cyrena. On the evidence I am disposed to correlate this deposit with that of Barnwell.

Let us compare the conclusions which have been drawn from an examination of this deposit with those arrived at by Mr. A. J. Jukes- Browne respecting the age of the valley of the Rhee, which he thinks of a later age than any of the other tributary valleys of the Cam. If I understand him rightly, he considers the gravel at Barnwell, which is about seven miles below Barrington, to be the oldest "terrace"-gravel in the district; for he does not apply that term to the still older "Observatory" gravel. And he thinks it "possible" (p. 68) that the gravels about Foulmire and Foxton were deposited about the same time as those about Barnwell and Trumpington; but he says that, "on the whole, it seems likely that they belong to a somewhat later period."

As to the age of the Foxton and Foulmire gravels, if the two are to be regarded as contemporary (upon which point I have no opinion to offer), the argument from equality of level is rather in favour of the Foxton gravel being of the same age as that of Barrington. But the deposit at Barrington is, in my opinion, due to the ancient Rhee, and it contains a mammalian fauna similar to that of Barnwell, certainly an ancient one; and consequently the Rhee must still occupy a very ancient line of drainage. The absence from it of