186 REPORT — 1856. 



Pomeridian, Cadent, and Veryent Series {Upper Helderherg, Ilamillon, and Che- 

 mung Groups). — These three natural, physical groups of strata, though characterized 

 by many peculiar fossils, are much less completely insulated from each other by 

 their species, than are the formations below them. It is remarkable that they are 

 related almost as intimately to the Silurian-Ludlow formation of England, and to 

 its continental equivalents, as to the European Devonian strata. Only two out of 

 all the Pomeridian species seem to be European ; but the general fades of the 

 fauna is as much Silurian as Devonian. The number of species common to the 

 Pomeridian and the Cadent rocks, is even less than the number which in England 

 pass upward from the Ludlow into the Devonian. Guided by numerical proportion 

 only, we might be justified in drawing the Silurian-Devonian line, — if the attempt 

 at recognition of the Silurian and Devonian, as independent systems, is legitimate 

 at all for the Appalachian basin, — at the boundary of the Pomeridian and the 

 Cadent. Mr. Hall, v\'ho was the first to promulgate explicitly this view of the 

 joint Silurian and Devonian affinities of the American Pomeridian and later strata, 

 reminds us, that in England there is a fusion amounting to 25 percent, of Silurian- 

 Ludlow fossils with Devonian in the rocks of Devonshire, or 10 per cent, of all the 

 Devonian species described by Professor Phillips. He justly says, " there is no 

 such mingling of species in the American formations." The older members of the 

 American Association of geologists will recollect, that, from an early day, the author, 

 in fellowship with his brother W. B. Rogers, contended, that we should not look for 

 a true equivalence between the formations of the American and European basins, 

 nor hope to discover either the same physical or the same palaeontological breaks 

 on both sides of the Atlantic ; and that therefore we were forbidden by the rules of 

 a sound philosophy to apply a European nomenclature to the American formations. 



Out of more than 220 or 230 species from the Cadent and Vergent (Hamilton 

 and Chemung) strata, about 20 are recognizable as European, Silurian and Devo- 

 nian forms, though Mr. Hall reduces the list to 12. He thinks that the organic 

 remains of the Cadent series are more closely related to those of the Ludlow forma- 

 tion of England, than to the European Devonian. M. De Verneuil recognizes 39 

 species of the Pomeridian, Cadent, and Vergent series, as belonging to the Silurian 

 and Devonian rocks of Continental Europe. Mr. Hall is unable to appreciate the 

 evidence which Avould place all these deposits in parallelism with the Devonian. 



From all the foregoing facts and statements, we arrive at this general inference, 

 that upon both palaeontological and physical evidence, there is no well-marked Silu- 

 rian-Devonian break discernible in the North American basin, no proof of an epoch 

 of general interruption in the life-stream, with wide crust-disturbance in the middle 

 palaeozoic ages, such as that which in earlier times, in the morning of the palseozoic 

 day, at the Cambro- Silurian transition, revolutionized alike the entire extent of the 

 American and European areas both in their inhabitants and in their physical geo- 

 graphy. 



