No. 380.] DEVONIAN PTYCTODONTIDA. 559 
limestone, with Ptyctodus extending both above and below this 
level. The State Quarry fish-bed is held by Professor Calvin ! 
to represent a later horizon than the Cedar Valley limestone, 
its anomalous relations leading him to the conclusion “that it 
was deposited unconformably upon the Cedar Valley limestone 
after the lapse of a considerable erosion period.” The evidence 
of invertebrate remains indicates that “the relations of the 
State Quarry limestone are with the Upper and not with the 
Middle Devonian, as is the case with the Cedar Valley beds.” 
Certainly the vertebrate fauna occurring here is unparalleled 
elsewhere in the Devonian, but in the assemblage we note the 
same species of Ptyctodus and Dinichthys as are found at 
Milwaukee and Rock Island, and probably also Heteracanthus. 
Where, now, shall the Milwaukee horizon be placed in the 
series? The strata here are divisible into two formations, the 
lowermost being the fish-bearing cement rock, and the upper- 
most a soft shale apparently destitute of vertebrate remains. 
Dr. Stuart Weller,? who has made a study of the invertebrates, 
finds that those from the lower formation are apparently most 
closely related to the typical eastern Hamilton fauna, as repre- 
sented in New York state, although there are a few forms 
which seem to represent the Iowa faunas. The upper formation 
has an abundant and well-preserved fauna, very different from 
that below. It is not the New York Hamilton fauna, but 
appears to be intimately related to some of the Iowa Devonian 
assemblages. With these generalizations vertebrate evidence 
stands in substantial agreement. Through Rhynchodus, Palæo- 
mylus, and primitive Dinichthyids, the hydraulic limestone 
fauna is related to that of the eastern province, dating back even 
to the Corniferous of Ohio. The Chimeeroids give it a stamp 
of antiquity, suggesting that a westward migration took place 
during the early part of the Devonian as far as Wisconsin, but 
not crossing the Mississippi Valley until the Middle Devonian. 
The Milwaukee beds show the first traces of encroachment from 
the east, the Rock Island locality a somewhat later, and the 
State Quarry limestone the last of all, with its horde of Upper 
1 Ann. Rep. Towa Geol. Survey, vol. vii, pp- 78, 79, 1897. 
2 Ann. N. Y. Acad. Sci., vol. xi, p. 117, I 
