21. Buff to pinkish argillaceous shale, with fossils, and a 22. Massive-bedded, siliceous limestone; weathering rough 23.* Bluish black limestone in massive strata, that break Fossils: Near the summit specimens were found that 1. Quartzite.. SUMMARY OF SECTION. 2. Limestone and shales (argillaceous and arenaceous)- 3. Massive limestone 125 1,570 1,430 350 1,450 3,000 4,800 At the horizon of Nos. 2 and 3 of the section, the Olenellus or Middle Cambrian fauna occurs; a fauna whose stratigraphic position is known in several sections. The next well-marked grouping of fossils occurs in No. 21, where, in the section and at a corresponding horizon in the Pioche section, the species mentioned in No. 21 were found. Of this fauna the two following species occur in the collection from Mt. Stephens, viz: Zacanthoides spinosus and Bathyuriscus Howelli. The same type of fauna occurs in the Cambrian section of the House range, at Antelope Spring, Western Utah, where, of the species found at Mt. Stephens, there occur: Agnostus interstrictus and Olenoides Nevadensis. Acrotreta gemma is found in No. 2, in the Highland section, near Pioche, Nevada, and it ranges up into the Upper Cambrian, in the Eureka District. Hyolithellus micans, although a common Middle Cambrian species, has not been identified, heretofore, west of New York. Of the eight species found at Mt. Stephens, six are stratigraphically located in the Cambrian system. Two speciesOgygia?? Klotzi and Ptychoparia Cordillera-are unknown to me from any other locality. * Quite a fauna occurs in 23, as found one mile farther south on the line of section. F The next superior fauna to the Olenoides of No. 21, is that occurring in No. 23, of the Highland section. It is of Upper Cambrian or Potsdam age, and contains: Bellerophon antiquatus, Pleurotomaria (3 undetermined species), Hyolithes (3 new species), Dicellocephalus Pepinensis, Dicellocephalus (type of D. Minnesotensis), Dicellocephalus sp., Ptychoparia (Euloma? dissimilis, Ptychoparia sp.?, Arethusina Americana, Illænurus sp.?. Of this fauna two species are identical with those from the higher Potsdam fauna at Eureka, viz: Ptychoparia (E.?) dissimilis and Arethusina? Americana; and Bellerophon antiquatus and Dicellocephalus Pepinensis occur in the Upper Potsdam sandstone of Wisconsin. The presence of the Pleurotomaria-like shells and the species just mentioned correlates the fauna with that of the upper horizon of the Potsdam faunas of Wisconsin and Nevada.* From the data mentioned I am led to the conclusion that the Mt. Stephens fauna described by Dr. Rominger should be referred to about the horizon of the upper portion of the Middle Cambrian fauna. This correlation, united with the discovery of the Olenellus fauna by Dr. George M. Dawson, in 1885, near Kicking Horse Pass, on the line of the Canadian Pacific railway, leads me to think that the Middle Cambrian fauna will be found to extend all along the western side of the great Keweenawan continental area, from Southern Nevada far into British America, and that that area will be found to belong to one geologic and faunal province of the Cambrian system. As Dr. Rominger has described nearly all the forms from Mt. Stephens as new to science it is necessary for me to review his work, since I have otherwise identified them in my work on the Middle Cambrian fauna.‡ He describes the new genus, Embolimus, and five new species of trilobites, viz: Ogygia Klotzi, O. serrata, Embolimus spinosa, E. rotundata and Conocephalites Cordillera. He also identifies Monocephalus Salteri? Billings, Bathyurus?, Agnostus ("compare A. integer Barr.") and the genera Orthis, Obolella, Kutorgina, Leptæna?, Metoptoma and Hyolithes. Embolimus.-The generic name Embolimus was given by Westwood to a genus of Hymenoptera in 1833.§ It was spelled Embolemus by Westwood and was corrected by Professor Agassiz in the Nomenclator Zoologicus The first species named under this genus by Dr. Rominger, Embolimus spinosa, was described as Olenoides spinosus in * Loc. cit., p. 35. + This Journal, III, vol. xxxiii, pp. 139–157, 1886. U. S. Geol. Survey, Bull. No. 30, 1886. Phil. Mag., II, 1833. 1886, and the second species, Embolimus rotundatus, as Bathyuriscus Howelli.+ When studying the Georgia fauna, in 1885, I found that the genus Olenoides was probably the same as the genus Dorypyge of Dames. Wishing more material for comparison I left all the species under the genus Olenoides. A large, fine species of the genus Olenoides was collected in the Cambrian shales of Northern Alabama, in 1886, which proved conclusively that Dorypyge was founded on a species congeneric with the type of Olenoides. I then recognized that the species Olenoides typicalis, O. spinosus, O. levis and O. flagricaudatus formed a distinct generic group, which I was having drawings prepared to illustrate when Dr. Rominger's paper appeared. As the generic name proposed by him is preoccupied, I now propose the name Zacanthoides, including in it: Z. typicalis, Z. spinosus, Z. levis and Z. flagricaudatus. The species remaining under Olenoides are O. Nevadensis, O. Marcoui, O. quadriceps and O. Wasatchensis. By a comparison of specimens I found that Embolimus spinosa Rom.=Zacanthoides spinosus Walcott, Embolimus rotunduta Rom.=Bathyuriscus Howelli Walcott, Ogygia serrata=Olenoides Nevadensis Meek; and that Conocephalites Cordillera Rom. = Ptychoparia Cordillera Rom. (sp.), and Ogygia?? Klotzi Rom. are new to the previously known Cambrian fauna. Zacanthoides spinosus Walcott, 1886=Embolimus spinosa Rominger, 1887.-This is a strongly marked species and occurs at Pioche and Eureka, Nevada, and in the collections from Mt. Stephens. Bathyuriscus Howelli_ Walcott, 18863=Embolimus rotundatus Rominger, 1887.-In the type figure of this species one segment has been forced beneath the head, a fact that was overlooked in the original specimen. A comparison of specimens from Mt. Stephens with the type from Pioche, Nevada, shows them to be specifically identical. Olenoides Nevadensis Meek= Ogygia serrata Rominger. This fine species is the type of the genus Olenoides; and a comparison of the specimens from Mt. Stephens with the type specimens leaves no doubt in my mind as to their specific identity. Ptychoparia Cordillera Rominger.-A specimen of this species, 23mm in length, has nineteen segments in the thorax and in this respect is similar to Ptychoparia Piochensis Walcott, from the same horizon, at Pioche, Nevada. The head, * U. S. Geol. Survey, Bull. No. 30, p. 184, Plate XXV, fig. 6. + Loc. cit., p. 216, Plate XXX, figs. 2, 2a. Loc. cit., p. 221. $ U. S. Geol. Survey, Bull. No. 30, Plate XXX, fig. 2. however, is unlike that of the latter, being more closely related to that of P. Kingi Meek. Ogygia? Klotzi Rominger. This is a fine, large species, and distinct from any known to me from the Cambrian terrane. It is more a type of the second fauna than of the first ; and its reference to the genus Ogygia is in accord with its general characters. It differs, however, in the important feature of having an ocular ridge extending from the anterior margin of the eye to the dorsal furrow, beside the glabella. The palpebral lobe is also more narrow and elongate than the eye of most species referred to Ogygia. All other parts of the head, thorax and pygidium relate it more closely to Ogygia than to any other genus. The oldest known species of the genus, 0. Selwyni Salter, from the Arenig terrane of Wales, is not quite so closely related in form to O.? Klotzi as to the O. Buchi from the Llandeilo terrane. It is unusual that a genus, showing so little variation from Ogygia, occurs at a much lower horizon in an area separated by over 5,000 miles, from the area where the species of Ogygia flourished at a later period in geologic history. Agnostus interstrictus White-Agnostus Rominger. This species of Agnostus is very abundant at Antelope Spring, Utah, where it is associated with Olenoides Nevadensis, as at Mt. Stephens. Acrotreta gemma Billings.-The broad, low form of this species occurs compressed in the shaly slate. The specimens. at hand are poor, but they appear to be identical with those from the Cambrian horizon at Pioche, Nevada. Kutorgina Prospectensis Walcott?.-A fragment of a species of Kutorgina, closely related to K. Prospectensis, occurs on the slate in association with Ptychoparia Cordillera. It is not improbable that it represents a new species. Hyolithellus micans Billings.-Black, shiny, concentrically striated or smooth, compressed tubes occur in the shale with the trilobites, that appear to be identical with H. micans of the Middle Cambrian fauna of New York, Vermont and Canada. The "slender stems," mentioned by Dr. Rominger, may be the same as the slender shells of this species which appear like compressed stems formed of shiny carbonaceous matter. It is doubtful what the specimen identified as Menocephalus Salteri? is. It may be the young of Bathyuriscus Howelli. The specimen figured as Bathyurus? is too badly defined to identify it. It certainly does not belong to the genus BathyuOf the remaining genera mentioned by Dr. Rominger I do not find any traces in the material before me with the exception of a fragment of a species of Orthis. rus. ART. XVII.-History of Changes in the Mt. Loa Craters; by JAMES D. DANA. [Continued from page 112.] RELATIONS OF KILAUEA TO MT. LOA. THE position of Kilauea "on the flanks of Mt. Loa," 9500 feet below the level of the summit, plainly suggests the idea of its later and dependent origin. If the two were begun at the same time, why, it is naturally asked, should not Kilauea have approximately the same size as Mt. Loa? With the same time to grow in, and a distance between the two nearly equal to that between Kea and Loa, and a crater as large and still active, would it have stopped at less than one-third the height and have raised its summit only 300 feet, at the best, above the Mt. Loa slopes? Several of the islands, Oahu, Molokai, Maui, and perhaps also Kauai, consist of two volcanoes united at base, or are volcanically twins; and Hawaii is a double twin, one couplet consisting of Kohala and Kea, and the other of Hualalai and Loa, provided Kilauea is subordinate to Mt. Loa. In all the twins the eastern of the two combined volcanic mountains is the larger. But Kilauea, although the eastern on Hawaii and the easternmost of the whole group, is one of the smallest. The greater size of the eastern volcano in a couplet has come from its continuing longer in action; and this is proved not simply by the size, but also by the evidence of long extinction, and therefore long exposure to denuding agents, in the western mountain; that is by the depth and extent of the valleys of erosion, the time-marks, over it.* There is other evidence also * As this evidence of the lapse of time is important, I here cite a few sentences from the chapter in my Exploring Expedition Geological Report, on the "Origin of the Valleys and Ridges of the Pacific Islands." pp. 379-392. "Mount Loa, whose sides are still flooded with lavas at intervals, has but one or two streamlets over all its slopes. and the surface has none of the deep valleys common about other summits. Volcanic action has had a smoothing effect, and by its continuation to this time, the waters have had scarcely a chance to make a beginning in denudation. Mount Kea, which has been extinct for a long period, has a succession of valleys on its windward or rainy side which are several hundred feet deep at the coast and gradually diminish upward, extending in general about half or two-thirds of the way to the summit. But to westward it has dry declivities, which are comparatively even at base, with little running water. Α direct connection is thus evinced between a windward exposure and the existence of valleys. And we observe also that the time since volcanic action ceased is approximately or relatively indicated; for it has been long enough for the valleys to have advanced only part way to the summit. Degradation from running water would of course commence on such slopes [windward slopes] at the foot of the mountain, where the waters are necessarily more abundant and more powerful in denuding action, in consequence of their gradual accumulation on their descent. "Haleakala, or eastern Maui, offers the same facts as Mount Kea, indicating the same relation between the features of the surface and the climate of the dif |