12 LIFE OF THE PLEISTOCENE 



deposits of the lake stages, as no data are now available for this purpose. The 

 Unios were probably taken from deposits of the Toleston stage. Some of the 

 gastropods were evidently from the Hammond or Englewood stages. 



The following species were identified for Prof. Marcy, who collected them 

 in stratum number 7 of his Evanston section. 



Galba palustris Physa warreniana 



Galba caper ata Ancylns species 



Galba reflexa Goniobasis livescens 



Planorbis trivolvis Pleurocera elevalum 



1899. Salisbury and alden. 18 — In this publication the authors make refer- 

 ence to the presence or absence of life in the several lake stages. 



Glenwood Stage (page 39) 

 "No satisfactory evidence of life has been found in the waters of the lake 

 at the Glenwood stage. This is as would be expected in waters mostly derived 

 from the melting of the great ice-sheet. " 



Post-Glenwood Low Water Stage (page 40) 



Reference is made to an interval of emergence preceding the Calumet stage 

 but no life is recorded. 



Calumet Stage (page 43) 



"In connection with the evidence of a withdrawal of the water from the Chi- 

 cago plain at the close of the Glenwood stage, and its consequent submergence 

 by the waters of the Calumet stage, the finding of evidences of life in these 

 lake deposits is of especial interest. The occurrence of shells in the Calumet 

 beach deposits at Summit and near New Buffalo, Michigan, has been reported, 

 but no definite information has been secured concerning them. The only place 

 where definite evidence of life has been found about Chicago is at the farm 

 of Mr. J. H. Welch, about one and one-half miles southwest of Chicago Lawn. 

 The Calumet shore-line was spoken of as being marked by a well-developed 

 ridge of sand and gravel swinging in a broad curve from Summit southwestward 

 about the north end of the Blue Island ridge. In Mr. Welch's field, just north- 

 west of the point where this ridge is cut by the Belt Railway, there have been 

 found numerous molluscan shells, and one specimen of coral. An examination 

 of these specimens showed them, without exception, to be of marine species, 

 whose present range is between Prince Edward Island and the West Indies. 

 With the specimens which could be identified there were many fragments so 

 well worn and thoroughly perforated as not to permit of identification. The 

 character of the evidence which these shells seem to afford is of such a radical 

 nature as to excite great interest, and conclusions must be drawn with extreme 

 caution. 



18 Bull. Geol. Soc. Chicago, I. 



