BBLOIT FORMATION 185 



at Dubuque, Iowa, is preferably joined to the Maquoketa series with four 

 other faunal zones. 



The reasons for choosing the name Beloit formation is obvious, the 

 stratigraphic and faunal succession having been long well presented* 

 from the locality of Beloit, Wisconsin. The line of demarcation at the 

 top of the so-called Trenton — that is, the Beloit formation — had been 

 well enforced there by Chamberlin. His use of the term Trenton was 

 clearly the same as that employed in the "lead region" proper to the 

 west. I had established by four successive trials or seasons' work that 

 the five faunal and stratigraphic zones, as I had learned them at Minne- 

 apolis, namely, (1) the Minneapolis limestone (or BufE bed), (2) the 

 Bellerophon bed, (3) the Stictoporella bed, (4) the Stictopora bed, and 

 (5) the Fucoid bed, in ascending order, are the equivalents of the Buff 

 limestone (1), Glass rock (2, 3), Brown rock (4), and Green rock (5) 

 of the "lead region" of southwestern Wisconsin,! and of the Lower Buff 

 (1), Lower Blue (2, 3), Upper Buff (4), and Upper Blue bed (5) of the 

 so-called Trenton in the Beloit district. The term Beloit appeared to be 

 well designed to replace the term Trenton, as it had been generally ad- 

 hered to in Wisconsin for over forty years. 



Eegarding further the demarcation of Trenton and Galena, Lapham 

 writes in 1851 of the Galena limestone :J 



"It is a soft yellowish, magnesian limestone, very fully described in the 

 ■report of the United States geologists for 1839, as well as by Mr. Hodge and 

 others at an earlier day. It is usually identified in distant localities by the 

 occurrence of a peculiar fossil coral, resembling the Coscinopora sulcata of 

 Goldfuss, the tubes of which are sometimes filled with lead." 



This lead coral, as it is called, is known to be Beceptaculites oweni. 

 Hall. 



Again, James Hall, as early as 1847,§ described Orthis suicequata, Con., 

 from the Blue limestone which he afterwards called Trenton, at Mineral 

 Point, and this fossil appears to have never been referred by any author 

 to the Galena. I have observed in the field that the demarcation of the 

 Beloit formation from the Galena can be drawn between the zone of 

 Orthis subcequata. Con., and that of Beceptaculites. These fossils are 

 common and easily observable, and the demarcation line is a very per- 

 sistent one, none better occurring in the Galena series. Since this forma- 



* T. C. Chamberlin : Geology of Wisconsin, vol. ii, 1877, p. 290. 

 t J. D. Whitney: Geology of Wisconsin, vol. 1, 1861, p. 253. 



% J. W. Poster and J. D. Whitney : Geology of the Lake Superior Land District, pt. 2, 

 p. 169. 



§ Paleontology of New York, vol. 1, 1847, p. 118. 



