302 Scientific Proceedings, Royal Dublin Society. 
suggestive of mammillary chalcedonic growth. In some instances 
the whole section is transversely constricted at irregular intervals 
as though segmented. The length of the segment shown in the 
figure (fig. 6) is 5 mm. 
Combining the information we have obtained, it 
is clear that the form of our fossil is at present that 
of a flattened band with much thickened margins, 
but whether this is original or not is by no means 
certain. Quite possibly the pristine shape was cylin- 
drical, and in that case the fossil may merely repre- 
sent a cylindrical cavity which has been filled up 
with silica and deformed by pressure or perhaps a 
corroded and subsequently silicified sponge spicule 
like those of the glass rope sponge Hyalonema. 
The shape of the tranverse sections, however, is 
difficult to account for on such supposition. A cylin- 
drical tube under the pressure which gave rise to 
cleavage in the slate would be converted into a flat 
band of elliptical section, and would not be lemnis- 
cate as in our examples. On the other hand it may 
be the silicified remains of some organism such as an 
Annelid or perhaps of a plant. Its appearance, 
however, is more worm than plant-like, and I would 
hazard the conjecture that it may be another trace Fic. 6. 
of the same organism that produced the markings ,,honsitcinal sec. 
known as Oldhamia. The dimensions are consistent **tictions ( 7°)- 
with such a view; both are probably worm-markings ; both occur 
in the same rocks in the same locality. ‘The new fossil requires 
an independent name, and I propose to call it Pucksia Mac Henryi. 
‘“‘Pucksia ” is a mere collocation of letters recalling the place of 
occurrence. The specific name is a tribute to my colleague, 
Mr. MacHenry, of the Geological Survey. 
The slate in which Pucksia occurs is found on microscopic 
examination to consist almost entirely of scales of white mica, 
lying of course with their flat faces parallel to the planes oi 
cleavage. 
A chemical analysis of the slate yielded the results given in 
column I. Its composition approaches very closely that of a 
phyllite analysed for Gumbel by Schwager (Roth. Chemische 
