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VIII.—On the Structure and Affinities of Metaclepsydropsis duplex (Williamson). 
By W. T. Gordon, M.A., B.A., D.Sc., Falconer Fellow of Edinburgh University, 
Lecturer in Paleontology, Edinburgh University. Communicated by Professor 
JAMES GEIKIE, D.C.L., LL.D., etc. (With Four Plates.) 
(Read July 3, 1911. MS. received July 28,1911. Issued separately December 18, 1911.) 
INTRODUCTION. 
While collecting specimens of Diplolabis rémeri (Solms) at Pettycur about three 
years ago, I discovered several blocks of stone containing numerous petrified frag- 
ments of another Zygopterid fern—Metaclepsydropsis duplex (Williamson). Two of 
the blocks were found to be parts of one large mass, and the petrifactions could be 
traced from the one block into the other. In size the complete mass must have been 
about 3 feet x 2 feet x 2 feet. The larger portion had to be broken into two before it 
was possible to remove it. Another block containing similar specimens was obtained 
later, but the preservation was so poor that the whole of the material was discarded. 
The Pettycur plants are usually preserved by an infiltration of calcareous material, 
chiefly carbonate of lime, but in these blocks the petrifying material was siliceous. 
This silica was present in two forms—chalcedony and crystalline quartz. (As a result, 
hollow stems had the appearance of agates, generally with a crystalline centre.) The 
exterior had been more or less weathered, and the specimens stood out on the surface, 
their tissues being perfectly visible, and giving a lace-like appearance to the surface of 
the blocks. 
As the occurrence of Diplolabis rémerz was a new record from a British source, and 
as the specimens could be more easily examined (since thin sections are more readily 
prepared from calcareous than from siliceous material), I decided to finish my work on 
that genus before proceeding with a systematic investigation of the silicified specimens 
of Metaclepsydropsis duplex. 
On looking over the specimens, however, about a year after they had been collected, 
I noticed, among the petioles, a fragment of what appeared to be a fern stem. ‘Two 
sections were prepared from it, and the length was ascertained by cutting that part of 
the block into pieces 4 to # inch thick. The same stem was followed into another 
part of the block, and its extent in that direction also determined. The total length of 
| this stem fragment was about 8 inches; it was hollow in the centre, and throughout its 
length no petioles or roots were emitted. 
: When this part of the block was cut up it was found to be so dark that no structure 
could be observed; in the hope that exposure to the atmosphere would soon weather 
the surfaces and so render the specimens visible, another part was sawn into pieces 
TRANS. ROY. SOC. EDIN., VOL. XLVIII. PART I. (NO. 8). 26 
