88‘ Wisconsin Academy of Sciences, Arts, and Letters. 
underlying the Lodi shale member of the Trempealeau formation. 
As described by Winchell the St. Lawrence limestone member at 
the type locality consists of grayish magnesian limestones, mottled 
with red and yellowish brown blotches and more or less profusely 
speckled with the green grains of glauconite, in layers 2 to 18 
inches thick and aggregating a total thickness of between 14 and 
15 feet. Under it is a shaly bed, 18 feet of which was observed 
by W. 0. Hotchkiss and the writer in 1915 in a ravine north of 
the quarry. The latter exposure did not extend down to the top 
of the Franconia which probably underlies the Trempealeau in 
the valley of Minnesota River as elsewhere. Whether the Fran¬ 
conia is present here or not the observed shale bed is lithologically 
at least like the bed that is found at many places in Wisconsin 
at the base of the Trempealeau and usually beneath the calcareo- 
magnesian zone that is correlated with the typical St. Lawrence 
limestone or dolomite. 
Regarding the propriety of the latter correlation it would be 
amply warranted by the similarity of lithologic characters alone— 
especially the likeness in the sequence and thickness of the litho¬ 
logic units concerned. But we have corroborating fossil evidence 
that with the lithologic evidence of the rocks themselves settles 
the question beyond all reasonable doubt. Fossils are seldom plen¬ 
tiful in the St. Lawrence limestone and only rarely are they in a 
good state of preservation. Despite these disadvantages a consid¬ 
erable fauna from this zone has finally accumulated. More im¬ 
portant is the fact that this fauna includes a number of character¬ 
istic species that are sufficiently distinctive to be recognized even 
in poor condition. Nearly always this zone affords some brachio- 
pods, particularly a form of Billingsella that we have not yet suc¬ 
ceeded in distinguishing from B. coloradoensis —a. common lower 
Franconia shell. Also a variety of Dicellomus politus, a species 
otherwise not found above the basal layers of the Franconia. With 
these usually is the Finkelnhurgia osceola corrugata which so far 
seems confined to this zone. Perhaps a surer but rarer guide fossil 
is a large trilobite that may be the species described by Walcott 
under the name Dikelocephalus vanhornei. Specimens of all of 
these four species rewarded a half hour’s search in the quarry at 
St. Lawrence, Minn. 
In Dane and Iowa counties, Wisconsin, the St. Lawrence dolo¬ 
mite is notable for certain interesting additions to its more usual 
Second Ann. Rept. Geol. and Nat. Hist. Sur. Minnesota, p. 152. 
