268 LIFE OF THE PLEISTOCENE 



the Mississippi River at upper end of Clarksville, may have been derived from 

 post-Kansan deposits. 



Two records of molluscan fossils from Callaway County, Missouri, 77 * ap- 

 pear referable to the Yarmouth interval, occurring in post-Kansan strata. 

 The first record apparently represents an old stream bed in which many land 

 shells, washed from the shore, are mixed with the few fluviatile species. The 

 second record is in typical Kansan loess and the species are all terrestrial. Of 

 these deposits Greger says: "The first place visited was an excavation on the 

 east bank of Middle River, a short distance below the point of its entrance into 

 the gorge of the Missouri. At a depth of 26 feet below the level of the flood- 

 plain of the Missouri River, in a black, sticky clay, the following species were 

 gathered: 



Polygyra profunda Succinea ovalis 



albolabris Gastrodonia ligera 



thyroides Jlelicina occulta 



elevata Pyramidula solitaria 

 clausa " alternata 



apprcssa " perspectha 



inflecla Helicodiscus parallelus 



fratema Campeloma subsolidutn 



monodon Pleurocera species 



hirsuta Mtiscullum transversum 



"The second locality examined was an exposure of typical loess in the gov- 

 ernment quarry a short distance above the town of Mokane on the M.K. & 

 T.R.R. The full section of strata exposed in the quarry face measures approxi- 

 mately 70 feet; rising abruptly from the flood-plain of the river, the Jefferson 

 City formation (Ordovician) presents a precipitous face of 60 feet followed by 

 a layer of tough, bluish clay, interspersed with worn fragments of limestone; 

 upon this bed of clay is deposited a layer of loess that varies in thickness but 

 having probably an average of 9 feet. The loess is capped with a layer of soil 

 rich in humus and supports a flora typical of the Missouri Bluff region. 



"While occasional specimens of the species listed were found throughout the 

 entire thickness of the loess, it was only in a thin zone, about 16 inches from 

 the base, that they were collected in abundance, in fact they are so abundant 

 in this zone as to attract attention from the highway below, by the white line 

 they present at the top of the quarry, being even more pronounced than the 

 Ordovician-Pleistocene contact. " 



It is probable that the loess deposit represents more or less continuous de- 

 position from post-Kansan to comparatively recent times. The band of 



" a Greger, Nautilus, XXX, pp. 64-66, 1916. 



