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PROGRESS OF MICROSCOPICAL SCIENCE. 
amined, it will be observed that although it sometimes completely 
lines the interior of the cup, it more often occurs only in patches ; and 
that, while some of the interstices are blocked up, there are others 
that remain open, and this not as the consequence of friction or 
weathering, but as the result of fossilization. It is, however, in some 
of the sponges of the Oolite that we see this infilling of the interstices 
most distinctly, in some of the cylindrical forms especially, the whole 
of the sponge, except its summit, appearing as though invested by a 
sheath, but which, were it really of the nature of a true epitheca, as in 
the Zoantliaria, it would be difficult to comprehend how the functions of 
the animal were carried on. It is more than probable that this struc- 
ture is nothing more than the cast of the impression or mould of the 
outer surface of the sarcode of the sponge, perhaps slightly thickened, 
but it is not constantly present even in the same species. For ex- 
ample, there is a small cylindrical sponge, not unfrequent in the Coral 
Rag, at Bullington Green, near Oxford, in which more or less of this 
so-called epitlieca is met with in some individuals, while the greater 
number show nothing of the kind. It appears, therefore, that the 
epitheca is sometimes only a result of fossilization, and is sometimes 
probably the cast of the outer surface of the sarcode which has left its 
impress on the mould ; that it is absent in the earlier and growing 
stages of the sponge, and is not constantly present in the matured in- 
dividuals of those species in which it occurs ; and, moreover, that it 
sometimes results from the contact of foreign bodies, in consequence 
of the increased density of tissue which such bodies are apt to produce. 
Its value, therefore, even as a specific character, is not great. 
Microscopic Fossils in Irish Chalk. — At a meeting of the Eoyal Irish 
Geological Society, on June 12th, Professor Hull, F.E.S., exhibited 
two slices of Chalk from County Antrim, showing under the micro- 
scope its essentially foraminiferous structure. On comparing the forms 
with those in Ehrenberg’s ‘ Mikrogeologie,’ Professor Traquair and 
the an th or were able to identify at least five genera, namely, Fotalia, Tex- 
tularia, Planulina, Nodosaria, and Globigerina — this last named being, 
as in the Atlantic mud, the most abundant ; and, in fact, constituting 
the greater part of the mass of the rock. The cross-section of the 
spine of an Echinus, and other forms of doubtful affinities, were also 
observed. The shells were nearly all preserved in calcite, and bound 
together by impalpable carbonate of lime. The slices were made by 
Mr. Jordan, of the Museum of Practical Geology. Mr. Hull called 
attention to the fact that the Foraminifera of the Chalk of the north 
of Ireland had scarcely received any attention from paleontologists. 
This, he considered, might be partly attributed to the unusually in- 
durated character of the stone, which rendered it almost impossible to 
extract Foraminifers by washing. This quality, however, was favour- 
able to the preparation of thin slices for microscopic examination; 
and Professor Rupert Jones had kindly undertaken to examine slices 
of the Antrim Chalk for comparison with those forms now under 
investigation by himself and Mr. Parker. 
Microscopic Organisms found on Inland Ice. — Dr. Berggren has 
communicated a notice of these organisms to the { Geological Maga- 
