324 



LIFE OF THE PLEISTOCENE 



has cut through one of the delta terraces so common in Cayuga Valley." A 

 vertical section is shown below: 



Drift 20-30 feet 



Gravel and sand several inches. 



Fossiliferous clay 5-8 feet. 



Boulder clay 10-15 feet. 



Devonian shales 10 feet above lake level. 



The lower boulder clay probably representing the Illinoian till, is oxidized' 

 indicating a period of erosion. The fossils, mostly mollusks, are imbedded in 

 a slaty blue clay, loose and peaty at the base, but becoming more compact 

 toward the center and upper parts. The lower, peaty deposit is composed 

 almost wholly of plant remains. These have not yet been identified owing to 

 their very imperfect state of preservation. It would be of great interest to 

 compare these plants with those found at Toronto in supposedly equivalent 

 beds. The mollusks obtained from this deposit have been determined as 

 follows: 



x Anodonta grand is x Valvata tricarinata 



" grandis footiana x Amnicola limosa 



" marginala x Pkysa keterostropha 



x Lampsilis luteola x Planorbis antrosus ( = bicarina!us) 



x " ventricosa " deflectus 



x Sphaerium sulcatum { = simile) " lentus ( = trivolvis?) 



x Pisidium compressum x " parvus 



" virginicum x Galba elodes 



x Campeloma decisum " palustris 



Comparing the above list with the Don beds at Toronto, we find that 12 

 species out of 18, or two-thirds, are common to both localities (an x in the above 

 list signifies that the species is found in the Don beds). The difference is purely 

 one of habitat, the Cayuga Lake deposit representing the quieter waters of a 

 lake, such as the Cayuga of today, while the Toronto mollusks lived on the 

 shores of, or in an estuary near the rougher waters of the ancient Lake Ontario. 

 It is interesting to note that at the present time all of the above species are 

 living in Cayuga Lake. 



Rich and Filmer, 178a in a study of the gorge of Six Mile Creek, near Ithaca, 

 find evidences of three glacial stages and two interglacial intervals. Their 

 interpretation includes (pages 73-74): 



1. Preglacial time. 



2. First glacial epoch. 



3. First interglacial epoch. 



4. Second glacial epoch. 



5. Second interglacial epoch. 



178a Journ. Geol., XXIII, pp. 59-80, 1915. 



