PREGLACIAL CONDITIONS AND LIFE 215 



*Mephitis orlhostichus Cope *Mustela dihtviana Cope 



* " obtusatus Cope Gulo luscus (Linn.) 



* " leptops Cope *Lulra rhoadsii Cope 



CANIDAE 



Canis latrans Say *Canis latidentatus (Cope) 



* " priscolatrans Cope " occidentalis Rich. (=/»/>».?) 



* " cineroargentatus Schreber Dinocyon species 



FELIDAE 



*Machairodus gracilis Cope *Felis inexpcctatus (Cope) 



* mercer ii Cope " eyra Desm. 



* " calcaralus Cope 



4. SUMMARY 



Preglacial Condition of the Glaciated Area. Previous to the Glacial Period 

 the region now occupied by the Great Lakes formed an immense river valley 

 comparable to that of the Mississippi, the outlet being possibly by way of the 

 St. Lawrence Valley. The watershed of the country was at this time quite 

 different from that of the present, many streams flowing northward and 

 emptying into the large Laurentian River. The land was also much higher 

 then than now, and mam- of the rivers (the Hudson, St. Lawrence, and others) 

 extended seaward and formed great canyons which are now deeply buried 

 beneath the ocean. 



Preglacial Biota. The life which existed prior to the ice age was different 

 in many respects from that which occupies the same territory today. The 

 plants experienced little or no change. Of the 23 species listed in the previous 

 catalog, but one is doubtfully extinct. The mollusks have probably remained 

 much the same, altho the land forms might contain some extinct races if 

 the record was complete. The fresh water species (with the exception of 

 the problematical casts from the Fish-house clay beds in New Jersey) are 

 identical with living forms. During the long period from the Cretaceous and 

 thru the Tertiary Period the fresh water shells, and especially the naiades, 

 spread over the eastern and southeastern part of the United States, probably 

 by way of the river systems which connected with the preglacial Laurentian 

 River. The 14 species of insects are all extinct. 



Of the 86 vertebrates, 64 are extinct, or over 74 percent. Several families, 

 as the sloths, the horses and the camels, are represented by a number of species. 

 These families, as well as the proboscidians, have become entirely extinct, as 

 far as the region under consideration is concerned. 



