Williams.] FAUNAL DISSECTION OF THE DEVONIAN. 89 
cal Chemung fauna, the Ithaca form is characteristic and much more 
common and has in the later literatures become the type of that 
species. 
These remarks will serve to express the present knowledge regard- 
ingthe actual distinguishing features of the fauna of the typical Che- 
mung formation. The difficulty found in making the definition more 
accurate comes from the great uncertainty as to the precision with 
which the limits of the fauna have been discriminated. 
In many reported Chemung lists of species uncertainty is presented, 
both as to the identification of Spirifer disjunctus and as to the exact 
stratigraphical horizon from which the species came. 
The present paper can therefore go no further in precision of defi- 
nition of this fauna; and attention is here directed to the great need 
of more accurate statistics regarding the individual faunules of the 
upper extension of the marine Devonian faunas. These statistics can 
be obtained by local collectors living in regions of outcrops of Che- 
mung rocks, who will render a service to science by furnishing accu- 
rate lists of the species, with statistics as to the exact locality and 
zone and the relative abundance of the species in each faunule. 
RECURRENCE OF THE TROPIDOLEPTUS FAUNA IN THE EPOCH 
OF THE SPIRIFER DISJUNCTUS FAUNA. 
Report of a recurrent Hamilton fauna in the midst of the rocks of 
the Ithaca formation was made in Bulletin No. 3 of the IT. S. Geo- 
logical Survey, p. 15. 
Mention was made also of Tropidoleptus and other Hamilton species 
occurring in Owego at a horizon high up in the Chemung. The full 
importance of these cases was not appreciated at the time of their first 
announcement. Recently the facts have been stated in detail and 
may be restated here: 
We have positive evidence of a colony of the Tropidoleptus fauna within ;it 
least 50 feet of the typical horizon of the Chemung formation in Chemung 
County, and also in the midst of the Chemung, or Spirifer disjunctus, fauna at 
Owego, as I announced in 1884." 
These evidences of the Tropidoleptus fauna are so clear that if we were to find 
them in an isolated region, we should have no hesitation in calling the forma- 
tion holding them Hamilton, except that a few species of much later age are 
associated with them. 
The typical species of the Tropidoleptus fauna are such as — 
Tropidoleptus carinatus (abundant). 
Amboccelia umhonata (abundant). 
Phacops rana (rare, but with several specimens I 
a Bull. U. S. Geol. Survey No. 3, 1884, p. :.'4; also Proc. Am Asm,,-. A.dv. Sci., Vol. XX XIV. L886,p 
226. This is the stage A 6 + of the Tropidoleptus fauna, called in thai paper Middle Devonian 
fauna A; also p. 230. 
