GEOLOGICAL SURVEY OF THE TERRITORIES. 433 



Not witli standing- tlie resemblance of sonic of these fossils to Devonian 

 formsj and the fact that scarcely any of the species can be identified 

 beyond doubt with forms peculiar to the Carboniferous, I nuist regard 

 the whole as belonging to the lower part of the lower Carboniferous. 

 It is extremely improbable that in a collection containing so many 

 brachiopods there would be no Atrypa, Strophodonta, Peiitameroid, and 

 other Devonian and older types, if the rock belonged to the Devonian. 

 The entire absence of any strictlj' Devonian and older types of corals, 

 crinoids, Lamellebranchs, &c., also favors the conclusion that this 

 formation belongs to the Carboniferous, which conclusion is also sup- 

 ported by the specific affinities, if not even by the specific identity, of 

 some of the species of Sph ifer, Productus, Chonetes^ Retzia, &c. 



In looking over the collections from these localities, I have been im- 

 pressed with the similarity of their general facies (without being quite 

 sure that any of the species are identical) to the fauna of the Waverly 

 group of Ohio, now known to belong to the Carboniferous. At the 

 same time that I would refer the beds from which these fossils were 

 obtained to the Carboniferous, it should be remarked that we have every 

 reason to believe that tliey belong to a lower horizon in the series than 

 those from which nearly all of the collections from "Old Baldy," Mon- 

 tana, were obtained ; also, than the fossiliferous beds on the divide be- 

 tween Eoss Fork and Lincoln Valley, Montana. 



LyonlliU. — The fossils from Lyon Hill, Oi>hir, East CaQon, Utah, are 

 of Carboniferous age, but it is not possible to determine, owing to the 

 small number and injperfect condition of the specimens, the particular 

 horizon in that system to which they belong. 



Swan Valley. — A few specimens from Swan Valley, Idaho, have been 

 })laced provisionally in the Carboniferous list, but they are very frag- 

 mentary and difficult to make out, and may belong to rocks of some 

 other age. 



Behceen Ross ForJc and Lincoln Valley. — The species from the divide 

 between Eoss Fork and Lincoln Valley, marked with an asterisk in the 

 list, are nearly all very small fossils, and occur crowded together in 

 such great numbers that all the specimerts in the collection (including 

 many individuals of some species) were broken from a few fragments of 

 the matrix, perhaps altogether not more than one-tenth of a cubic foot 

 in volume. Some seven or eight of the thirty-two or thirty-three sjiecies 

 thus found, .seem to be in all respects, so far as the specimens afford the 

 means of comparison, identical with forms occurring at the celebrated 

 Spergen Hill locality, near Bloomington, Indiana, while five or six others, 

 if not more, may be only varieties of Spergen Hill species ; ami nearly all 

 of the remainder belong to genera Ibund at that locality, and so closely 

 resemble in their small size and other characters, that they may be re- 

 garded as representative forms. 



The occurrence of so many apparently identical and representative 

 species of such a peculiar groui> of pigmy forms, all crowded together 

 in the same way, at these two widely se])arated localities, is certainly a 

 very remarkable and interesting fact ; and one, too, so tar as yet known, 

 without a i)arallel in all of our American rocks. It is all the more 

 curious because not a single species of these little fossils has hitherto 

 been identified from any intermediate locality west of Iowa and Mis 

 souri, and even there the few species that have been found generally 

 occur isolated among larger species. In comparing two collections of 

 such peculiar fossils from localities so remotely separated, many inter- 

 esting questions bearing on the geogra]>hical distribution of species 

 naturally suggest themselves. Adopting the view that each species, in 



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