head of the North Fork of Shade Creek, which were determined by Edwin Kirk, of the United States Geological Survey, as Diplograptus sp. and assigned by him to the Normanskill. The exact locality (28AMt261) is 1 mile N. 172° W. from "Hug" boundary triangulation station (McCann Hill). These fossils come from a narrow band of slate, directly above the Upper Cambrian limestone but directly below a group of rocks composed of argillite and chert, of Middle Devonian age. This Ordovician slate is too small to show on the scale of the accompanying map but can be discriminated and mapped on a larger scale. The occurrence is here recorded, for the benefit of later workers in this area. Most of the Carboniferous fossils collected by Cairnes occurred in rocks that were dominantly noncalcareous, although some of the upper Mississippian rocks evidently contain thin beds of limestone, as they do at Calico Bluff, on the Yukon. The Carboniferous fossils of the boundary were studied originally by G. H. Girty, of the United States Geological Survey, and those collected from latitude 66° southward to the Yukon have recently been reexamined by him. Three of these collections from the vicinity of Ettrain Creek, which occur in limestone and are now referred by Girty to the Permian, are separately listed under the Tahkandit (Permian) limestone. (See p. 129.) All the others, as revised, are listed below: XIV s 43: Favosites sp. Crinoidal fragments. Fenestella, several sp. Hemitrypa? sp. Spirifer cf. S. marcoui. Martinia? sp. XV c 40: Fenestella sp. Polypora sp. Cleiothyridina cf. C. pectenifera. XVI j 9: Zaphrentis sp. Marginifera? cf. M. involuta. XVI k 10: Fenestella sp. Pinnatopora (Acanthocladia) sp. Cystodictya sp. Hustedia cf. H. indica. Zaphrentis sp. Fenestella sp. Productus cf. P. tenuistriatus. Productus cf. P. inflatus. Myalina cf. M. keokuk. XVI 19: Fenestella sp. Chonetes sp. Marginifera? cf. M. involuta. Reticularia cf. R. lineata. Spirifer cf. S. nikitini. Spirifer sp. Aviculipecten sp. Aviculipecten? sp. XVII a 38, 39: Chonetes sp. XVII a, b 33: Batostomella sp. Productus cf. P. tenuistriatus. Productus cf. P. curvirostris. Productus sp. Leiorhynchus sp. Paraparchites sp. XVII b 39: Zaphrentis. Chaetetes? sp. Lithostrotion? sp. XVII e 27: Productus cf. P. curvirostris. Productus cf. P. pustulatus. Productus cf. P. cancriniformis Camarophoria cf. C. explanata XVII j 30: Amplexus sp. Productus cf. P. gruenewaldti. Marginifera? cf. M. involuta. XIX b 3: Chonetes cf. C. variolatus. Productus cf. P. porrectus. Productus cf. P. humboldti. Productus cf. P. wallacianus Productus sp. Spirifer cf. S. cameratus. Spirifer cf. S. nikitini. XIX b c 35 to 37: Chonetes cf. C. variolatus. Productus cf. P. humboldti. Productus cf. P. wallacianus. Spirifer cf. S. nikitini. XIX c d 30, 31, 32: Michelinia sp. Zaphrentis, 2 sp. Batostomella sp. Polypora, 3 sp. Derbya? sp. Rhipidomella sp. Chonetes sp. Productus semireticulatus. Productus cf. P. pustulatus. Productus cf. P. cancriniformis. Productus sp. Marginifera cf. M. involuta. Spirifer cf. S. fasciger. Spirifer cf. S. nikitini. Spirifer cf. S. tastubensis. Spirifer cf. S. condor. Squamularia cf. S. perplexa. Spiriferina sp. Cleiothyridiana cf. C. pectenifera. Hustedia cf. H. indica. Aviculipecten sp. Pleurotomaria sp. Amplexus sp. XIX e 30: Favosites sp. Zaphrentis sp. Polypora sp. Batostomella sp. Lingula cf. L. albapinensis. Rhipidomella sp. Schuchertella cf. S. chemungensis. Chonetes cf. C. geinitzianus. Chonetes cf. C. variolatus. Chonetes sp. Productus cf. P. porrectus. Productus cf. P. cancriniformis. Productus cf. P. fasciatus. Productus cf. P. juresanensis. Marginifera? cf. M. involuta. Spirifer sp. Squamularia cf. S. perplexa. Aviculipecten, 2 sp. Pleurotomaria sp. Paraparchites sp. XIX i 4: Chonetes cf. C. ostiolatus. Productus cf. P. humboldti. Camarotoechia sp. Girty's latest statement regarding the probable age and correlation of the fauna above listed is given herewith: I find it possible to repeat at this time most of what I wrote to Mr. Cairnes in 1912-something that does not always happen. As regards the age of this 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 horiOne 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. zons. 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 preservation 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 listswould 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 j 9: Obolus sp. Lingulella sp. Acrothele cf. A. coriacea Linnarsson. Acrotreta, 2 sp. |
