148 
PE0E. T. ETJPEET JOKES—OEIGIN AND 
univalves crammed with shells from the shallows may have been 
buried in deep muds; * * * § and sharks, like crocodiles, are said to 
swallow pebbles, and these evacuated or disgorged, or left on 
the decomposition of the carcase, would fall in strange regions; hut 
ice alone could carry the heterogeneous mass of blocks and sand 
found at Purley, or the block of coal found in the Chalk of Bent.f 
Besides the drifted shallow-water organisms found in the Chalk, 
the many other fossilised shells, Echinoderms, etc., are, in the 
late Dr. J. Gwyn Jeffreys’ opinion (and as an experienced Con- 
chologist he could speak with much authority), really such as 
must have lived in comparatively shallow water ;J that is, the 
abyssal fauna of the Atlantic is by no means identical with the 
Chalk fauna, although some genera of Echinoderms and Sponges 
dredged up by the “ Challenger” Expedition appear to be identical 
in the two, and several, having biological alliance, are interesting 
analogues. 
Post-Cretaceous Changes .—The further history of the Cretaceous 
Ocean is complicated. Some parts of it, if not all, were silted up 
and became shallow seas, lagoons, and dry land in time ; and the 
gradation of one or another set of strata above the Chalk proper into 
Tertiary beds, and their long-continued Lower, Middle, and Upper 
successions, are traceable in one region or another. In Western 
Europe, however, the Chalk became the floor of a shallow sea, with 
shelly beds of the Thanet Sands at one place, and at another sea¬ 
weeds rooting themselves in its flat-planed surface (at Beading, New¬ 
bury, etc.), and oyster-beds preceding the local fresh-water conditions. 
Previous to this, however, and again and again afterwards, the 
Chalk and its associated strata were strained and bent and broken, 
lifted in one place and let down in another, by the lateral crush 
and oscillatory movements of the Earth’s crust, leaving heights to be 
denuded and hollows to be filled up, until the geographical condi¬ 
tions became what we see them to he now, and the geological sections 
such as I have described (page 144). To what extent the xitlantic 
basin represents the Post-Cretaceous subsidences, §—how far it 
participated in the sinking not only of a part of the Cretaceous 
basin, but of the subsequent Eocene and Miocene seas, which 
stretched across W. and E., and have left the Mediterranean as 
a limited relic of their last stages,—it is difficult to say. We are 
not concerned at present with these considerations, except in 
remembering that the present “ Atlantic ooze ” (with its grey and 
red clays, and diatomaceous and radiolarian silts) is a thick and 
still-increasing covering of former sea-beds, and differs in many and 
important respects from the White Chalk to which in books it is 
often likened. 
* ‘ Quart. Journ. Geol. Soc.,’ vol. xvi, p. 324. 
f See Godwin-Austen’s interesting paper on this subject in the 1 Quart. Journ. 
Geol. Soc.,’ vol. xvi, p. 326. 
J Dixon’s ‘ Geology of Sussex,’ 2nd ed., p. xxiii. 
§ Dr. W. B. Carpenter has treated of this subject—see his Lecture, Brit. 
Assoc. Meeting, Brighton, 1872. 
