634 SLUART WELLER 
either one or the other of the two additional conspicuous species 
at the locality, and from careful examination and comparison of 
the specimens, descriptions and figures, it seems most probable 
that the species occurring in such numbers in zone 5A ” is the C. 
littont of these authors. 
The sixth division is zone 54 *3, and has a fauna quite differ- 
ent from any of those below. Leptena rhomboidalis is the most 
abundant species. Some of the additional conspicuous species 
are Chonetes deflecta and Chonetes pusilla, which are apparently 
variations of a single species, Pholidastrophia nacrea, Athyris vittata 
of the type common at the falls of the Ohio, Phacops rana, Para- 
cyclas elliptica and Paracyclas lirata. As a whole the fauna is of 
a Hamilton facies, but is more like the Hamilton fauna at the 
falls of the Ohio than the typical New York fauna. Orthis 
(Schizophoria) towensis is an uncommon species which is con- 
spicuous in the Devonian faunas of Iowa, but is absent from the 
New York faunas until after the incursion of the Chemung faunas 
from the west. 
The seventh and last division is zone 5A *5,and may be termed 
the Chonetes coronata zone. The bed is made up of multitudes 
of individuals of Chonetes coronata, with perhaps one-tenth as 
many individuals of 7vopidoleptus carinatus. Both of these species 
are peculiar forms and are characteristic of the New York Hamil- 
ton. They appear suddenly both in the New York and the Illinois 
localities without any known forerunners. Tvopidoleptus carina- 
tus is an abundant species in the South American Devonian 
faunas, and Chonetes coronata is of a type otherwise unknown in 
North America, but common in South America, where it is 
represented by C. arcet Ulr., C. riickt Ulr., and other species. There 
is evidence in the Hamilton fauna of the east-American province 
of an immigration from the southern hemisphere which did not 
affect the western Devonian faunas. The details of this epoch 
in Devonian history are not yet fully understood, but the pres- 
ence of this Chonetes coronata and Tropidoleptus fauna marks the 
point where this immigration first made itself felt in the south- 
ern Illinois region. 
