Carboniferous Limestone Trilobites. 447 
Cephalothorax unknown. 
Pygidiwm :—22 mm. broad and 16 mm. long ; smooth, semicircular, 
one-fourth broader than long, axis convex, 7 mm. wide, one-third the 
breadth of the pygidium at its anterior border, smooth, moderately 
elevated, axal furrows broad; where decorticated showing evidence 
of the coalescence of about 12 somites or rings, 12 mm. long, taper- 
ing to a blunt extremity, which does not reach to the posterior 
margin, but leaves a smooth border 4 mm. wide behind it; pleuree 
slightly convex, very indistinctly furrowed, margin entire, smooth, 
broad; general surface smooth and destitute of ornamentation of any 
kind, save a simple rib-like furrow and ridge where the pygidium 
unites with the free thoracic segments. 
Formation :—Carboniferous Limestone. 
Locality :—Moneenalion Commons, Upper; Co. Dublin, From 
the Museum of the Geological Survey of Ireland, Dublin. Kindly 
lent by Prof. E. Hull, M.A., LL.D., F.R.S., Director. 
The specimen here described is the same recorded by Mr. W. H. 
Baily, F.L.S., F.G.8., M.R.LA., Acting Paleontologist to the Geo- 
logical Survey of Ireland, in the Explanatory Memoir to Sheets 102 
and 112 (p. 19), as “ Phillipsia Brongniarti,” and was obtained from 
the Upper Limestones on the south side of Dublin, at Moneenalion 
Commons Upper, about one mile 8.E. of Castle Bagot (Sheet 111). 
in the Explanation to Sheet No. 111, Mr. G. V. Du Noyer wrote 
(p. 21), ‘‘‘The general aspect of the limestone varies between that 
of a palish and a dark-gray compact rock; it is usually very fetid, 
and contains layers of chert, while the shales are not so common as 
in the black beds at the bottom part of the group.” 
«Some beds are very fossiliferous, and the Trilobite (Grifithides) 
is not uncommon in them; others consist almost entirely of crinoid 
fragments, large Producte occurring sometimes in layers.” 
The specimen under consideration is imbedded in dark (almost 
black) fetid crystalline limestone, full of crinoidal fragments and of 
Brachiopoda. 
A careful comparison of this specimen with the pygidium described 
by Phillips (formerly called “ P. Brongniarti,” but now placed in the 
genus Griffithides under Phillips’s original name of obsoletus) has 
satisfied me that they cannot possibly be placed together. 
“ Ph. Brongniarti”” = G. obsoletus compared with Proetus levis. 
(a) Axis of pygidium nearly equal to (a) Axis less than one-third the entire 
half the breadth. breadth. 
(6) Axis extremely gibbous. (6) Axis but little elevated. 
(c) Pleure very convex. (c) Pleuree almost flat. 
(d) Axis and pleure very distinctly an- (d) Axis and pleure very nearly smooth. 
nulated. 
(e) Pygidium one-fourth broader than (e) Pygidium one-third broader than 
long. long. 
The fact of this- abdominal shield from Co. Dublin being so 
unlike any one belonging to Phillipsia or Griffithides, led me to 
compare it with those of other genera, and I was at once struck 
with its resemblance to the pygidia of Proetus. Seeing that Messrs. 
