1866. | Geology and Palzontology. * 279 
Professor Beyrich’s Oligocene division, makes use of this very 
marked result to urge the claim of the “Oligocene” to universal 
recognition as representing a period distinct from the Eocene. In 
a former chronicle * we have seen that Professor Reuss’s investiga- 
tions into the Foraminifera and Bryozoa do not support such a con- 
clusion ; but it is possible that this difference in the evidence yielded 
by these several classes of animals may be owing to the greater 
vertical range generally possessed by the more lowly organized 
animals. The practice of “counting heads” does not, however, 
find much favour amongst the more advanced paleontologists, and, 
as it seems to us, it can only be defended on the ground that, on a 
large scale, errors tend to neutralize one another. Dr. von Koenen 
has also omitted to reckon as Upper Eocene species those shells 
which have been found in Lower Oligocene and Middle Eocene 
deposits, and which therefore must have existed during the Upper 
Eocene period ; that is, of course, unless the universally accepted 
principle that such is the case be false ; if it be false, the onus pro- 
bandz lies with him. 
In the same number of the ‘Zeitschrift’ the late Dr. Oppel 
proposes the name “ Tithonic Stage” for the strata known to us as 
Portland, Purbeck, and Wealden. ‘This association under one name 
of the beds between the Neocomian and the Kimmeridge Clay will 
doubtless be useful in regions where the true freshwater Wealden 
and Purbeck beds do not exist; but it is very unlikely to be 
adopted in England. 
M. Barrande continues to defend his “ Colonies” with great 
vigour, and the third part of his ‘ Défense des Colonies’ is a large 
volume in itself. In it he treats at great length of the two upper 
members of his “ third fauna,” being stages G and H; but the only 
point of general interest is the conclusion that the fauna of these 
strata is not more nearly related to that of the Devonian system 
than are the faunas of the higher zones of the Upper Silurian 
formation in other regions, while the connection of the lower stages 
of this ‘third fauna” with the Devonian system is closer than that 
of the higher divisions G and H. ‘The question at issue between 
M. Barrande and his opponents is one of such complexity that we 
cannot attempt to discuss it; but it seems unfortunate that the 
term “colony” should be applied to a precursor of the main fauna, 
instead of to isolated branches given off by the parent. 
The pages of the ‘Reader’ have for some time past been 
adorned by a desultory discussion on Mr. Croll’s hypothesis, that 
the glacial submergence was a necessary result of the influence of the 
weight of the ice-sheet, which during the glacial period covered the 
northern parts of the globe, on the earth’s centre of gravity. Mr. 
Croll assumes, for purposes of illustration, that the ice in Greenland 
* «Quarterly Journal of Science,’ vol. i. p. 100. 
VOL, III. U 
