Fossils from Magnesian Limesto^ie. — Calvhi. 145 
been found in this formation in Iowa are, so far as known, a few 
traces of the stems of Crinoids found near McG-regor. " Whit- 
ney in Hall's Geology of Iowa, p. 337, speaking of indications of 
organic life in the Lower Magnesian limestone, says that "in 
Iowa, indeed, we have observed nothing of the kind." Owen 
seems to have been more fortunate than the other observers men- 
tioned, for in his report on the Geological Survey of Wisconsin, 
lova and Minnesota, p. 60, he enumerates a few genera that are 
represented in this formation, but does not cite localities. The 
EuomphaJus and Oj)hiIeta which he mentions, may be from the 
horizon of the Lower Magnesian limestone of Iowa; the trilo- 
bites referred to are probably from the LTpper Potsdam or St. 
Croix group as will be noted farther on. In the Geology of Wis- 
consin, Vol. IV, Whitfield describes a number of species from 
the Lower Magnesian limestone, but it is probable that the only 
species referable to the horizon of the formation in Iowa is his 
Euomphalus strongi which he says occurs in cherty beds in Rich- 
land county, Wisconsin. In the Geology of Minnesota, Final 
Report, Vol. i, pp. 222-223, Prof. Winchell mentions the discov- 
ery of organic remains in limestone of the same age as our Lower 
Magnesian. The fossils occur only in cherty beds and embrace 
the genera Orfhoceras, Ophileta and Pleurotoniaria. 
In all discussions relating to the fauna of the Lower Magne- 
sian limestone of Wisconsin, Iowa and Minnesota, it should be 
borne in mind that for many years geologists have confounded 
the St. Lawrence limestone, a member of the Potsdam or St. 
Croix series, with the Lower Magnesian. In the Geology of 
Minnesota, Final Report, Vol. .ii, pp. 1-4 to 22, Prof. Winchell 
gives the results of the latest investigations on this subject and 
points out the true relations of the long misunderstood St. Law- 
rence limestone. It is possible that all the species of Dlceloceph- 
alus, Conocephalites, Ilhiiiurus, and other forms associated 
with them, which have been credited to the Lower Magnesian 
limestone, have come from the St. Lawrence limestone and belong 
to a horizon below that of the Lower Magnesian. 
Within the past few years Mr. F. H. Luthe, an enthusiastic 
and intelligent amateur geologist, of McGregor, Iowa, has inves- 
tigated the fauna of the Lower Magnesian limestone of Clayton 
and Allamakee counties, and has brought to light an asseml)lage 
of forms of very great interest. Mr. Luthe has kindly placed 
