DEVONIAN AND MISSISSIPPIAN FAUNAS 2a) 
“ 
horizon, is scarcely or not at all recognizable beyond a short distance 
south of St. Louis. The fauna of these shaly Warsaw beds is more or 
less closely allied to that of the subjacent formations, but it contains 
numerous species which are quite distinct and some which are either 
identical with, or related to, members of the superjacent faunas. 
Subsequent to the Warsaw sedimentation the land to the north of 
the Mississippi Valley Basin was elevated. The Salem limestone 
which lies immediately above the Warsaw has a thickness of only 8 or 
to feet at Warsaw, IIl.,! where the formation consists of an impure, 
arenaceous limestone. To the south it increases in thickness to a 
maximum of about too feet, and is for the most part a very pure 
limestone, although magnesian layers are not unusual. The forma- 
tion extends eastward beneath the younger formations, and is again 
exposed in western Indiana, off the western shore of the old Cincinnati 
island. A notable feature of the formation is the presence in it, 
throughout its entire geographical extent, of more or less extensive 
odlitic beds. 
The fauna of the Salem limestone, commonly known as the Spergen 
Hill fauna, contains many diminutive forms, one of the most common 
species being Cliothyris hirsuta, which was present in a Kinderhook 
oolite at Burlington, Ia. Several small forms of Conocardium are also 
common in the fauna, one of the species, C. meekana, being somewhat 
closely allied to C. pulchellum from the same Kinderhook odlite. A 
comparison of the fauna with the Mississippian faunas of other parts 
of North America indicates a close relationship with certain faunas far 
to the northwest in Montana and Idaho. Meek? has recorded a fauna 
from a limestone in Idaho in which nearly one-half of the forms are 
identical with Spergen Hill species, and in the Yakinikak limestone? in 
northwestern Montana a similar fauna also occurs. ‘These limestones 
in Montana and Idaho are doubtless to be associated with the Madison 
limestone of the Yellowstone National Park, in which occurs a fauna 
having relationships with the Kinderhook of the Mississippi Valley, 
and especially with that of the Kinderhook oélite bed at Burlington, 
Ta., a relationship which may account for the partial recurrence in 
t [ll. State Geol. Surv., Bull. No. 8, p. go. 
2 Am. Jour. Sct. (3), V, 383- 
3 Bull. Geol. Soc. Am., XIII, 324. 
