276 The Ainerican Geologist. Nuvi-ihIkt, \s%:, 
the Lc Claire and the Onontlaga salt group. The Niagara is 
said to be recognized by the fossils Unljisitcs cnfeinildtus and 
Pciitdineriis ohIoiif/t(s. The Le Claire is said to be* "Gray, or 
whitish limestone, sometimes yellowish on fresh fracture. The 
Avhole mass is semi-crystalline and very porous, from solution 
and removal of fossils. It is sometimes so extremely and uni- 
forml}^ vesicular as to resemble the porous lavas or amygda- 
loids. The surface is harsh to the touch and on fresh frac- 
ture has the sharpness and harshness of a siliceous rock. It 
would nevertheless appear to be a magnesian limestone, but is 
rei)uted to make the best limestone in that ])art of the coun- 
try." The fossils reported are a small Sjtirifei\ a Sju'riijera 
or Athyris, a Peiitanieriis indistinguishable from P. occiden- 
talism, several gasteropods and some chambered shells. He adds 
that no complete collections were made. The Onondaga salt 
group or Salina formation is described as an evenly bedded, 
drab colored limestone, which affords rock for building pur- 
poses. 
In the American Journal of Science for May, 1802, A. H. 
Worthen stated it as his opinion that the formations called 
Onondaga and Le Claire by Hall were identical and that their 
characteristic beds were ff)und intercalated, and that they 
represented the upper Niagara. In the New York Kegents' 
report of 1864 Hall stated it as his conclusion that the Le 
Claire was of Niagara age, but still maintained that the beds 
he had called Onandaga overlie the Le Claire. In White's re- 
portf these representatives of the Upper Silurian are all placed 
under the title of Niagara group, HalTs Le Claire being men- 
tioned as synonymous in part, and the Onondaga or Salina 
is not mentioned at all. 
In McGee's Pleistocene history of northeastern Iowa,!; after 
the statement that Norton maintained HalTs division into Ni- 
agara and Le Claire, the opinion is expressed that, as no un- 
conformity is known and as the successive strata unquestion- 
ably represent continuous deposition, it is inexpedient to 
divide the series. 
In the Iowa report for 1892 a photographic plate is given 
showing apparent unconformity between the upper and middle 
*Hairs Geology of Iowa, vol. i, part 1, pp. 73, 75. 
tGeol. of Iowa, 1870, vol. i, p. 182. 
tEleventh Annual Rep. U. S. Gool. Surv.. 1889-90, p. 32.'). 
