CoLte—On Hemitrypa hibernica. 135 
membranacea, Phill., for the groundwork, and a microscopic coral 
or polyzoon for the superstructure.’”! 
This statement carried weight by its simplicity and directness, 
and practically abolished Hemitrypa as far as the British Isles 
were concerned. I prefer to make no comment on it, as Mr. 
Ulrich has already dealt with the matter with the necessary pre- 
cision (9, p. 354). Professor Nicholson, in 1879, in the second 
edition of his “Manual of Paleontology” (vol. i., p. 422), had 
given an account of Hemitrypa; but in the third edition (1889) 
the genus was excluded. Meanwhile, von Zittel (7, p. 601), 
basing his remarks upon Mr. Shrubsole’s Paper, had given wide 
circulation to the idea that Hemitrypa was a superfluous genus, 
adding that it might be a Fenestella in a particular state of 
preservation. Doubtless owing to a deficiency of materials, 
this author did not remark, as M‘Coy might have done, that if 
it was a Fenestelia, the specimens of that genus, hitherto regarded 
as typical, must be held to be all in an imperfect state of preserva- 
tion. 
Hence, with Mr. Kirwan’s interesting specimens before me, I 
felt that the simple process of cutting sections would set the 
question of the relations of the “sheath” at rest. Such sections, 
transparent or on smoothed surfaces of the rock, were exhibited at 
meetings of the Dublin Microscopical Club, where, from Dr. J. A. 
Scott and others, I gained valuable advice. They were amply 
sufficient to show that in Irish species of Hemitrypa the connexion 
between the two layers was fundamental and organic. 
But on the American continent the researches of Prout 
(8, p. 444; pl. 17, fig. 4) had long ago led to the formation of 
correct opinions. Under the name of Fenestella hemitrypa, he gave 
the earliest accurate description of the genus Hemitrypa. His 
specimen was from limestone of Lower Carboniferous age, St. 
Louis County, Missouri, and was fortunately well preserved. 
Prout showed that the ribs of this Fenestellid bore a row of “ pro- 
jecting tubercles separating two lines of pores, . . . these 
tubercles unite at top and form slightly waved ridges in the 
direction of the longitudinal ribs, between which the lines of cells 
*The same view was also emphasised by Mr. Shrubsole in dealing with British 
Silurian Fenestellide (Quart. Journ. Geol. Soc., vol. xxxvi. p. 242). 
