54 CONTRIBUTIONS TO DEVONIAN PALEONTOLOGY. [bull. 244. 
None of these species are abnormal to the fauna. The association 
of species is characteristic of the Nunda formation of New York, but 
there are a few species from a lower horizon. 
In the Virginia section the fauna occupies the zone of coarse shales 
succeeding the pure, line, smooth black shales, and from its strati- 
graphic position represents the fauna of the Nunda formation of New 
York. The rocks belong to the Romney and Jennings formations. 
The sequence of sedimentation is regular, and there is a gradual 
change from pure, fine-grained black shale up to coarser and more 
arenaceous shale. These conditions are characteristic of the Grainger 
shales in which occur the Buchiola speciosa fauna. 
Except for the greenish shale, 15 feet thick, of the Covington sec-« 
tion, there is scarcely a trace of the faunas characteristic of the richly 
fossiliferous Onondaga (Corniferous) and Hamilton formations of 
New York, and it is evident from the fauna that follows that its 
horizon is not lower than the Nunda of New York. The greenish 
shale (1382 B3) underlying the black shale with this fauna in the Cov- 
ington section contains a distinct fauna which is as follows: 
Faunule of greenish shale at Covington, Va. 
1. Schizophoria sp. I 3. Ambocoelia umbonata. 
2. Atrypa spinosa. | 4. Phacops rana. 
These species are indicative of a fauna ordinarily lower than the 
Nunda formation. a But the association of species alone, with the 
knowledge we now have of the range of the species of the Hamilton 
formation of New York, does not fix the age of this faunule with pre- 
cision, since it is known to recur above the Ithaca fauna, and after 
species characteristic of the Chemung have appeared. Thus the faunal 
analysis indicates, not a regular succession of diverse faunas, but an 
interrupted succession of several faunas, each of which is recognized 
in the normal New York series, but the observed order of which does 
not strictly correspond with that characteristic of the standard New 
York sections. 
It becomes necessary then to suppose interruption and replacement 
of faunas and a recurrence of early faunas at horizons above their 
(supposed) normal positions. This state of things has been elaborated 
in the study of the New York Devonian, but the detailed facts regard- 
ing these middle and southern Appalachian faunas is not sufficiently 
well known to make an exact correlation with the former possible at 
the present time. 
a See footnote on p. 86. 
