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255. On the genus Spirifera and its interrelations with the genera 
Spiriferina, Syringothyris. Cyrtia and Cyrtina. (Bull. Geol. Soc. 
Amer., vol. i, pp. 567, 568.) 1889. 
256. Some suggestions regarding the subdivision and grouping of 
the species usually included under the generic term Orthis, in accord- 
ance with external and internal characters and microscopic shell struct- 
ure. (Bull. Geol. Soc. Amer., vol. i, pp. 19—21. 1889. 
257. New Forms of Dictyospongidte from the rocks (j1 the Che- 
mung Group. Ninth Ann. Rept. State Geol. pp. 56 — 60. (Bull. 
Geol. Soc. Amer., vol. i, p. 22I) 1890. 
258. Review of "A Catalogue of North American Crustacea con- 
fined to the Non-trilobitic genera and species, by A. W. Vogdes." (The 
Financial and Alining Record, Feb. 22, 1890.) 
259. A Geological Map of the State of New York. (Trans. .\mer 
Inst. Min. Eng., Plattsburgh Meeting, Oct., pp. i — 7.) 1892. 
260. Preliminary Geological Map of New York exhibiting the 
structure of the State so far as known. Prepared under the direction 
of James Hall. State Geologist by W. J. McGee. 1894. 
NOTES ON THE DRIFT OF NORTHWESTERN 
IOWA.* 
By H. Foster B.\ik, Des Moines, Iowa. 
In northwestern Iowa and adjacent portions of South Da- 
kota and Minnesota there is a large V-shaped area with the 
apex pointing north lying between the Dakota and the Des 
Moines lobes of the later ice sheet. The area is bounded to 
the east and to the west by the first or Altamont moraine, 
which has been thought to mark the maximum extension of 
what is now known as the Wisconsin drift sheet. This area 
is covered by an extra-morainic drift sheet and it is the age 
of this drift and its associated deposits which it is proposed to 
discuss in this paper. 
This drift has been imperfectly known for some time and 
there are extant certain meager notes on it. In the reports 
of the Minnesota survey it has been described by Winchell and 
by Upham as shown in Murray and Noblest and Pipestone 
and Rock counties.? 
The drift was considered by the Minnesota geologists to 
*Read before the Iowa Academy of Science. 
tUpham: Final Rept. vol. I, p. 250. 
IWinchell, N. H.: Ibid., p. 543-545. 
