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fauna, I am in a curious dilemma, owing to the recurrence in the late Pennsylvanian of Russia of types of fossils that are more or less restricted to the Mississippian of the United States. Judged by our standard the fauna would be late. Pennsylvanian or even Permian; judged by the other it would be late Mississippian. Of course if an exact agreement were found with either, all uncertainty would instantly vanish, but nothing more is found than general resemblance. My identifications and comparisons as furnished to Cairnes would suggest a tentative preference for a Pennsylvanian or Permian age, though the formulas employed were in part at least merely descriptive and did not necessarily carry any strong implication of geologic age. My present feeling is the other way, that this fauna is probably Mississippian, though, I should add, it has scarcely any features in common with the typical Mississippian faunas of Iowa, Missouri, and other States. At present the only ground that is even approximately safe is that we apparently have two distinct faunas belonging in two distinct hori
One horizon is the Alaskan Permian; the other is older. Unfortunately we know little or nothing about the stratigraphic relations of the Cairnes collections; such knowledge would doubtless be a great aid to us in the present difficulty. The true positions of this fauna in the time scale seemingly must be left to future investigations-probably to a recognition of it in other areas where its relations to other faunas have been determined.
I should perhaps add that because I have designated three collections as Permian, I would not imply that all the rest belong to the other questionable fauna. A number of the residual collections are so poor in species or in preserration that no disposition of them can be made.
The original faunal lists prepared for Mr. Cairnes are returned herewith. I have checked the lists with the collections, species by species, and made a few changes in terminology. In the original lists the species are compared with those of Tschernyschew's “Gschelian" fauna. If I attempted to embody my present idea in the lists I would perhaps try to find comparable species in our Mississippian faunas. This would entail a great many changes in the lists would in fact give some of them an entirely new aspect. Under the conditions of uncertainty that exist, this seemed undesirable, and the names as they stand may well be taken to indicate specific resemblance without implying geologic age.
Limestone.—Cairnes, in his work along the international boundary, collected Cambrian, Ordovician, Silurian, and Devonian fossils from limestones of these ages but did not differentiate the limestones on his geologic map. Burling, in 1913, collected Cambrian and perhaps other Paleozoic fossils from limestone in the same area. Harrington, in 1909, collected Middle Devonian and Ordovician fossils from the limestone on the Tatonduk River near the boundary, and the writer in 1925 collected Middle Devonian and Silurian fossils from this same district. All the fossils from Paleozoic limestones that have not been differentiated in the geologic mapping are listed below.
Cambrian fossils collected by D. D. Cairnes:
XIX ; 9—Continued.
Agnostus, 2 sp.
Obolus (Westonia) cf. 0. stoneanus (Whitfield).
Foraminifera ? undetermined.
Three unidentified trilobites.
Micromitra (Iphidella) pannula (White) ?
Obolus, 2 sp.
Curticia ? sp.
XX i 34 :
Solenopleura, 3 sp. L. D. Burling, in 1912, made six collections: 4730, 4731, 4732, and 4733. Squaw Mountain north of Tatonduk River, international boundary. 4734 and 4689. Jones Ridge, north of Tatonduk River, international boundary.
C. E. Resser, of the United States National Museum, who has lately been studying this material, gave to the writer the following partial list of genera occurring in these collections: 4730, 4731, 4732, 4733, and 4734 :
Trilobites of several genera and species. 4689:
Eoorthis sp. All of Cairnes's Cambrian fossils, with the exception of collection XX i 34, which was believed to be possibly of Middle Cambrian age, were referred by Burling to the Upper Cambrian, and so far as the writer is aware no later work has been done on this material. Collection 4689, made by Burling, is referred by Resser to the upper part of the so-called “ Canadian system,” or, in the United States Geological Survey nomenclature, to the Beekmantown group of the Lower Ordovician series. Collections 4730 to 4734, also made by Burling, are referred by Resser to the Upper Cambrian of Ulrich, which in United States Geological Survey nomenclature is the lower part of the Upper Cambrian. Hence it would seem that the Upper Cambrian series is rather fully developed as marine limestones along the boundary.
Cairnes collected Ordovician fossils along the boundary but not within the area covered by this report, and lists of those fossils are therefore not here included. The fossils of Ordovician age collected
by Harrington in 1909 came from the gravel of the Tatonduk River near the boundary and consisted entirely of Columnaria alveolata. The presence of this species, of course, has little stratigraphic value, because the gravel in which it occurs may have been transported many miles.
Cairnes's Silurian fossils include 8 collections of middle Silurian age and 11 collections of upper Silurian age. Of the 8 middle Silurian collections, only 6 were obtained within the area covered by this report, and these are given herewith. The determinations were made by E. M. Kindle, of the Geological Survey of Canada. XIX s 28:
Pholidops cf. P. squamiformis Hall,
Illaenus cf. I. armatus Hall.
Illaenus cf. I. imperator Hall.
XVII h 13:
Camarotoechia cf. C. indianensis (Hall).
Farosites gothlandicus Lamarck.
Atrypa reticularis (Linnaeus). The single Silurian (1) collection made by the writer from the limestone of the Tatonduk River was examined by Edwin Kirk, of the United States National Museum. The locality of this collection and its fauna, as given by Kirk, follow: 25AMt168 (2064) :
Crinoid columnals. Cairnes's Devonian fossils also were determined by Kindle. They include, within the area here treated, 15 collections, of which 12 were assigned definitely to the Middle Devonian and were correlated with the Salmontrout limestone of the Porcupine River. The other three collections were believed to belong to some other horizon in the Devonian. The Middle Devonian fauna is listed below: XVII p 4, 5:
Cyphaspis cf. C. bellula.
Atrypa reticularis (Linnaeus).