256 Cincinnati Society of Natural History. 
of about 425 feet above low water mark in the Ohio river, at Cincinnati, 
O. My best specimens I found in equivalent strata at Hamilton and 
Morrowtown, O. 
ATACTOPORELLA oRTONI, Nicholson (Pl. XII., figs. 7, 7a). 
Cheetetes ortont, Nich., Quar. Jour. Geol. Soc., vol. xxx., p- 513, Pl. XXIX.., figs. 15-156, 
1874; Pal. Ohio, vol. ii., p. 211, Pl. XXII., figs. 3-30. 
poncieuin te (Peronopora) (?) ortonis Niche The Genus Wore), PD 22,85 APA elves 
gs. 4, 4a, 46, and 4d (not 4c). 
be detailed description of the exten characters of this well-known 
and beautiful little species is unnecessary, and I would do no more 
than simply mention it as an undoubted member of this genus, were I 
better satisfied with the way in which Dr. Nicholson has worked out 
its internal structure. He does not mention interstitial cells, although ~ 
in all of my sections of the species, I find more or less clear evidences 
of their having been present in large numbers. It is true that they 
are generally partially filled by a deposit of sclerenchyma, which, pos- 
sibly, in some cases, may have been so dense as to obliterate all traces 
of the numerous horizontal diaphrayms which my sections clearly 
show. I make no objection to his figure of a tangential section, since 
in most sections in which the fully matured characters of the zoarium, 
just below the surface, are laid bare, the interstitial spaces are, from all 
appearances, compact. In a few tangential sections, however, I was 
enabled to determine with certainty the outlines of the rather large 
and angular interstitial cells. ‘These were always shown to better ad- 
vantage in the monticules (PI. XII, fig. 7) which appear to be mainly 
occupied by them. The true zoccia have, in reality, very thin walls, 
which, so far as my observation has extended, are never thickened in- 
wardly. The same is true of perhaps all of the species of Atactoporelia, 
and in this peculiarity the genus seems to be unique, as I have never 
noticed such a character in any other of the numerous forms of the 
Monticuliporide. 
In his work on “ The Genus Monticulipora,” Dr. Nicholson claims to 
represent a vertical section of this species, on Plate III., to which I 
must object. The figure in question (4c), if it is at all a fair repro- 
duction of his section, almost certainly belongs to some other bryozoan, 
perhaps to a species of Leptotrypa. I therefore can understand why he 
should complain in the text of not being able to find cystoid diaphragms 
in his vertical sections. He could not have failed to see them had he 
such a section before him, as my vertical sections, which, by the way, 
are invariably cut from the same specimen that furnishes the tangential 
