692 A. C. LANE AND A. E. SEAMAN 
with the ‘‘ New red” Triassic sandstones, held by Jackson, Marcou,' 
and for a time Bell. But accepting its approximate equivalence and 
even continuity with the Potsdam, there still may be a question as 
to its exact horizon, which can not be exactly the same everywhere, 
and might be widely different. It is readily divided in outcrop and 
in wells into a redder and lower portion and a whiter upper portion. 
The line between the two may mark the epoch of submergence of 
the iron-bearing rocks, only a few islands of granite and quartzite, 
remaining exposed to erosion. In view of the uncertainty of the 
relation of the three parts of the Lake Superior sandstones, as used 
by Houghton, separate names seem to us likely to be useful, and we 
propose not only the term Freda sandstone for that west of the Copper 
Range, but the term Jacobsville (from Jacobsville where the famous 
quarries of Portage redstone occur) sandstone for that east of the 
Copper Range, and we suppose this term may apply to all the Lake 
Superior sandstone skirting the coast at intervals to Grand Island, 
while the term Munising sandstone is to apply to the upper 250 feet of 
Lake Superior sandstone which crosses the bluffs back of Munising, 
dips southerly, and is white or light colored. Houghton considered 
the upper ‘“‘gray sandstone” (700 feet ?) to be unconformable on 
the lower, dipping south to southeast, while the lower dips to the north. 
The upper part is well ripple-marked, cross-bedded, friable, with 
Fucoides (?) duplex and Lingulepis prima, and L. antiqua. Dike- 
locephalus misa (?), Dikelocephalus (Hall, Pl. XXIII, 3a-e, 4), and 
Lingulepis primijormis occur at Iron Mountain which Walcott told 
Lane was of the Ptychaspis zone. At Marquette Murray reports Pleu- 
rotomaria laurentina (?) and Scolithus and beds similar at Campment 
d’Ours close under the Trenton. At Limestone Mountain, below 
the fairly extensive Trenton fauna, are some conglomeritic beds 
before we come to the main mass of sandstone. Logan (followed by 
Grabau)? mainly on the strength of the (en)Campment d’Ours 
Island section concludes that the Lake Superior sandstone may 
“represent the Chazy, Calciferous, and Potsdam.”’ Beside the Camp- 
ment d’Ours Island section the Neebish well also indicates a great 
thinning of the section below the Trenton to the pre-Cambrian along 
St. Mary’s river.. But the question remains whether it is by a dis- 
t Bull. Geol. Soc. Trans., Vol. XXXII, p. 102. 
2B. G. S. A., Vol. XVII, pp. 582, 617. 
