694 R. W. RICHARDS AND G. R. MANSFIELD 
UPPER MISSISSIPPIAN LIMESTONE 
The Wells formation in southeastern Idaho rests in apparent 
conformity upon limestone of upper Mississippian age. In Utah, 
however, Blackwelder (1f) has observed an unconformity at this 
position in the section. These limestones represent an unnamed 
formation comprising about 1,130 feet of beds. Lithologically 
they are massive gray, light to dark colored, weathering white 
to light gray. Locally a dark shale zone is developed near 
the top about 15 feet thick. In places also chert nodules with 
concentric and irregular forms and streaks of chert are present. 
The limestones are sometimes specked with siderite and seamed 
with calcite or aragonite, and are abundantly fossiliferous in some 
horizons. The fauna includes large cup corals with many fine 
septa, Syringopora, Lithostrotion, Martinia, and Productus giganteus. 
The Martinias are found in a bed near the top of the formation. 
A fauna collected at Ross Fork—Lincoln Creek (Idaho) by Meek (17) 
and later by Girty (19e) at Swan Lake which is comparable to that 
of the Spergen limestone of the central basin region of the United 
States is included at the Swan Lake locality in the upper Missis- 
sippian limestone interval. 
The formation constitutes much of the Preuss Range and is 
well exposed in Meade Peak, the culminating point of that range. 
No complete section has been measured because of structural 
interruptions, but it is expected that future studies in the Ross 
Fork locality may afford a more favorable opportunity to obtain 
this, and the selection of a type locality for the formation is deferred 
for the present. 
The authors are also indebted to Dr. Girty for the following 
faunal list and comments: 
An interesting and varied fauna has in places been obtained from the upper 
part of the upper Mississippian. It is shown by the list of forms collected at 
Station ror. A short distance below this collection a new species of Martinia 
was found in countless numbers constituting a bed a foot thick. Very abundant 
also in local occurrences is a small variety of Productus giganteus. Large 
Zaphrentoid corals are likewise a feature of the upper Mississippian, often 
occurring associated with Syringopora and one or more species of Lithostrotion. 
These colonies are sometimes of great size. Here too is sometimes found an 
