Devonian Shales of Northern Ohio. 21 L 



the following statement regarding the affinities of the fish 

 fauna : 



" There are three genera of Genesee fishes which occur also in 

 the Ohio shale, one of them represented by an identical species. 

 These are : Glyptaspis, Aspidichthys, (Jallognathus serratus. 

 These three are in addition to IJinichthys, already mentioned, 

 making four in all, and I should not be surprised to find this 

 number increased with later discoveries." 



Conodonts are nearly everywhere common or abundant fossils 

 in the Huron shale. But it is desirable to defer the discussion 

 of their evidence until they have been more carefully studied. 

 The faunal evidence which has been presented represents a 

 limited number of species, but it is uniform and consistent in 

 indicating a Devonian horizon not later than Portage or Gene- 

 see. It is, on the other hand, irreconcilable with the overlap 

 hypothesis. If, as the advocates of the Mississippian age of the 

 Huron would perhaps claim, the Devonian species referred 

 to above are recurrent forms which persisted beyond the 

 limits of Devonian time, it is remarkable indeed that no 

 Carboniferous fossils are associated with them to attest their 

 transgression of the Devonian-Carboniferous boundary. The 

 absence of such fossils renders such an explanation untenable. 

 The rather close resemblance of the Huron and Cleveland 

 shales in lithologic features is paralleled by faunal likenesses 

 which are conspicuous in the conodonts and fishes. But there 

 are also some faunal differences as well as likenesses. Some 

 species have a restricted range comparable if not identical 

 with the limited upw r ard range of the large spherical concre- 

 tions which, characterize the Huron. Dinichthys hertzeri 

 belongs with the group of species which do not range above 

 the Huron shale. This species is known from the shore of 

 Lake Erie at Rye Beach* to central Kentucky. f It has, however, 

 never been found in the Cleveland shale although few if any 

 fish-bearing horizons in the world have been more persistently 

 searched by enthusiastic collectors than the Cleveland shale in 

 the Cuyahoga and Black River sections. Professor New- 

 berry's observation that the Cleveland shale fishes are in 

 general of small size as compared with those of the Huron 

 shale appears to be still valid. He wrote : 



" In the Huron shale, on the contrary, we find the remains of 

 fishes of enormous size, of most peculiar structure, and such as 

 clearly belong to the Old Red Sandstone fauna so f ullv described 

 by Hugh Miller.J 



* Branson, E. B. : Letter to the writer March 4, 1912. 

 t Kindle, E. M., this Journal, vol. xxxiii, p. 135, 1912. 

 X Newberry, J. S. : Report on the Geology of Erie County and the Islands, 

 Ohio Geol. Survey, vol. ii, pt. 1, 1874, p. 188. 



