é 
134 Scientific Proceedings, Royal Dublin Society. 
Fenestella fossula, and regarded the “ investing crust” as a parasite. 
He admitted that the agreement between the openings of the two 
layers was “interesting” and “remarkable.” This investigation 
was carried on with a hand-lens, and nothing was determined as 
to the nature of the outer layer. 
Having, in fact, certain preconceived ideas as to the characters 
of the Fenestellide, various authors regarded a superposed feature 
with suspicion ; but its rejection as an integral part of the organism 
was based upon very imperfect examination. 
Sir Richard Griffith, who had before him the specimens 
examined by M‘Coy, records Hemitrypa as a separate genus, the 
one well-recognized Irish species, H. hibernica, occurring in his 
lists in all the divisions of the Carboniferous Limestone (4, pp. 70, 
76, and 81). 
The late Mr. W. H. Baily (5, p. 107), describing drawings of 
Fenestella membranacea (ibid., pl. 87, fig. 26.), wrote, “ Portion of 
the upper or celluliferous surface, enlarged ; this, when removed, 
exhibits impressions corresponding with the condition of the fossil 
named Hemitrypa hibernica, M‘Coy.” But the drawing shows, in 
its lower part, merely raised casts of the fenestrules. A little pit, 
a very common feature, occurs in the summit of these, perhaps by 
the contraction of the mud that first infilled the hollows of the 
organism; and this gives a casual resemblance to M‘Coy’s figure 
(2, pl. xxix., fig. 7) of the outer surface of Hemitrypa. But, as we 
shall see later, the raised ring-like bodies in M‘Coy’s drawing are 
based upon an optical illusion. 
Mr. Baily continued to maintain the view that Hemitrypa was 
founded upon a mistake, despite the fact that M‘Coy’s specimens 
were close at hand in Dublin. Pencil-notes in his private copy of 
M‘Coy’s “ Synopsis” show that Mr. Baily regarded the type- 
specimen as the result of an encrustation upon Fenestella mem- 
branacea. 
This fact doubtless influenced Mr. G. W. Shrubsole (6, p. 281) 
during his review of the British Carboniferous Fenestellida. He 
asserts that the outer sheath of Hemitrypa is ‘without doubt a 
small coral common to the limestone, very similar to Flustra 
paimata, M‘Coy, the empty calices of which cover over and conceal 
the Fenestelia beneath. Hemitrypa, as we have seen, has Fenestella 
