426 Revleics — Cretaceous Series of Upper Missouri. 



members of the group renders it probable tbat the Mesozoic seas 

 spread further eastward than has hitherto been commonly supposed. 



II. At pages 211-236 Dr. Samuel Calvin, State Geologist, shows 

 that the old idea of the geological structure of North America 

 being destitute of " Chalk " is quite unfounded, as readers of the 

 American Journal of Science, Canadian Naturalist, Bulletin of the 

 American Geological Society, Science, the Reports of several Geo- 

 logical Surveys, and well-known works by Ehrenberg and F. 

 Roiner, might well know. He states that true "Chalk," soft and 

 white, made up of Foraminifera and Coccoliths, and without the 

 admixtui'e of mechanical sediments, has a thickness of at least 

 25 feet on the Sioux River in Iowa; and is 50 feet thick at Ponca 

 in Nebraska; at Saint Helena, further up the Missouri, 90 feet; at 

 Yankton in South Dakota, 130 feet ; and probably 200 feet at the 

 mouth of the Niobrara. Near the mouth of the Sioux it is repre- 

 sented by (from top) — (1) Chalk, 12 feet; (2) soft Inoceramus- 

 limestone, 12 feet; (3) Chalk, 12 feet. (See Mr. Bain's memoir, 

 p. 111.) 



Dr. Calvin (p. 115), having described the mode of occurrence of 

 the foraminiferal shells as being quite similar to that in the English 

 Chalk, proceeds to enumerate and discuss the various published, 

 notices that have indicated a rising and increasing knowledge of 

 this view, founded on the recognition of microscopic fossils in the 

 Cretaceous strata from various parts of North America. Thus 

 Prof. J. W. Bailey, in 1841. described some " prairie chalk " from 

 the North-west (see also Hitchcock's "Elementary Geology," new 

 edition, 1860, p. 382) ; Dr. Ch. G. Ehrenberg figured some 

 Foraminifera from the Chalk of Missouri and Mississippi, 1843, 

 and Bailey in 1844; Dr. F. Romer some from Texas, 1852, and 

 T. A. Conrad in 1857 ; F. B. Meek and F. V. Hayden described the 

 Cretaceous strata along the Missouri River, in 1859-61 ; Dr. C. A. 

 "White the Inoceramus-limestone of Iowa, in 1870 ; Dr. G. M. 

 Dawson the Chalk of Nebraska and Manitoba, 1874; Prof. R. T. 

 Hill, in 1888, 1889, and 1890, definitely gave the name of "Chalk" 

 to the soft calcareous beds of the Lower and Upper Cretaceous series 

 in Texas and Arkansas ; and Prof, S. W. Williston treated of the 

 Kansas Chalk in 1890. 



The more common of the Foraminifera of the North-American 

 Chalk, as figured by the various observers above referred to, appear 

 to be — 



1. Textilaria pygmma, d'Orbigny. G. M. Dawson, Canadian 

 Naturalist, vol. vii, 1874, p. 253, fig. h ; S. Calvin, Iowa Geol. 

 Survey, vol. iii, 1895, p. 226, pi. xix, fig. 7. This is rather common 

 in the Cretaceous and Tertiary deposits, and in existing seas. 



2. Textilaria globulosa, Ehrenberg. Bailey, Amer. Journ. Sci. 

 and Arts, vol. xli, 1841, p. 401, fig. 2 ; Calvin, Iowa Geol. Survey, 

 vol. iii, 1895, p. 225, pi. xix, fig. 5. This species, first described by 

 Ehrenberg, has a wide geographical range, chiefly in the Cretaceous 

 series. The localities whence the specimens figured by Ehrenberg 

 were obtained are — Cretaceous : Egypt, Syria, Arabia (?), France, 



