Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/745

Rh OF THE CARBONIFEROUS SERIES. 041 [America. — I am unwilling to lengthen this paper by reference to the succession of beds on the American continent, but think it proper to observe that, as Dr. Ferd. ltomer has pointed out, the marine stage, E, is fairly represented at the base of the Coal-measures in the United States *. In the lower beds of the productive Coal- measures in the western portion of the State of Kentucky occurs a small Lingula (L. umbonata, Cox), which Dr. Homer considers to be in all probability identical with L. mytiloides of Phillips ; and about 100 feet higher in the series, at Nolin Iron- works, several genera of Cephalopods also are found. Amongst these is Nautilus ferratus, Cox, which approaches very closely to, if it be not identical with, N. bilobatus, Sow., from the Carboniferous Limestone of Coalbrook- dale. In the State of Iowa, a band of marine limestone occurs about 20 feet above the " Concretionary Limestone " which marks the upper limit of the Carboniferous Limestone proper. It is separated from this latter by shales, sandstones, and a bed of coal 15 inches thick. In this limestone are found several species of Productus, a small Spirifer, a Nautilus, and the tail of a Trilobite t. Similar marine bands are found in the districts lying at the base of the pro- ductive Coal-measures, and may be regarded as referable to the horizon of the Lower Coal-measures of the British Isles. Even if America afforded no analogy as regards the succession of beds with that of Britain, it ought not to be considered as invali- dating the views here expressed. The British and continental areas are sufficiently large to form the basis for a classification of beds.] Part VI. (a) Conclusions regarding the Conditions of Deposition of Carboni- ferous /Strata drawn from the Characters of the Fossil Fauna. Amongst the varieties of remains of animals which have been found in various Carboniferous strata there are none upon which we can rely with so much confidence for information regarding the con- ditions of deposition as the Mollusca. Of those which lived in the Carboniferous period many of the genera, or their modifications, descend down to the present day ; so that we may determine their habits by actual observation, and, by inference, those of their prede- cessors. It is not so with the fishes. The placoids and ganoids of the Coal- period were, in all probability, like the sturgeon and other inhabi- tants of the Black Sea and the Caspian, migratory, and capable of living either in the open ocean, or of navigating the streams and plant-choked estuaries of the period ; so that they throw no light upon the condi- tions of deposition of the strata in which their remains are found. 'Geological Keport of Kentucky,' vol. iii. pp. 515, 51G (1857). t 'Keport on the Geological Survey of the State of Iov.a,' by J. Kail and J. D. Whitney, vol. i. p. 233 (1858).
 * Loc. supra cit. p. 604. Quoting MM. E. T. Cox and Leo Lesquereux,