296 
Aug. F. Foerste 
the Whitewater member of the Richmond in Indiana and Ohio. 
The species ranges, however, from the lower part of the Waynesville 
member to the top of the Whitewater member, on Manitoulin island^ 
and it occurs also in the fossiliferous layers near the middle of the 
Queenston clay shales, near Meaford, in Ontario. These Queens- 
ton shales are regarded as occupying the same time interval as the 
Whitewater member of the Richmond. 
Ulrich prepared a monograph on the various species of Tetradium, 
but the plates were destroyed by fire and the monograph was never 
published. The only remnant of this monograph is the inclusion 
of the name Tetradium approximatum in his list of fossils from the 
Cincinnati Group, and the reference of this species to his beds XIII 
and XIV. His beds XIII include the Arnheim, Waynesville, and 
Liberty members of the Richmond, while beds XIV included the 
Whitewater and Elkhorn members. Evidently Ulrich regarded 
Tetradium approximatum as ranging through a considerable part,, 
if not all, of the Richmond. 
In my own collecting, in the Richmond of Cincinnatian areas, 
I have found Tetradium to range from the base of the Clarksville 
division of the Waynesville member of the Richmond to the top of 
the Richmond. 
The term Tetradium approximatum evidently applies to the- 
common Richmond form, which has a wide geographical range, 
both in the United States and in Canada. It can not be said, how- 
ever, to have had any validity prior to the publication of Bassler’s. 
Index. It seems unfortunate that Hall’s casual illustration of an 
erratic specimen should give priority to the term Tetradium Ontario, 
but this actually is the case. 
Dania huronica, described from Drummond island by Edwards 
and Haime (Mon, d. Polyp, Foss, Terr, Pal., 1851, p, 275, pi, 18, 
fig, 2, 2a. 2b) must be regarded for the present as a problematical 
species. Although usually assumed as of Niagaran age, the 
corallites are described as scarcely attaining a diameter of one 
millimeter even in the case of the largest corallites. No Niagaran 
coral is known from Drummond island with corallites of such small 
dimensions. Specimens of Tetradium however occur in the Rich- 
mond along the northern shore of the island, and occasionally the 
septa are rather distant and occur approximately at the same- 
height across 6 to 20 of the exposed adjacent corallites. 
