POSTGLACIAL BIOTA OF THE GREAT LAKES REGION 195 



Berry). In Massachusetts a fossil flora indicates a subarctic climate, evidently 

 living not far south of the retreating glacier. A later deposit, not far distant, 

 indicates a temperate climate. The variation of climatic conditions as the 

 huge glacier retreated to the northward, is thus indicated by the remains of 

 life contained in the deposits left by the glacial waters. 



4. PERCENTAGE OF LIVING AND EXTINCT SPECIES 



Sixty-eight species of plants and 271 species of animals are represented 

 in the deposits overlying the Wisconsin drift. An analysis of this biota 

 shows that of the plants 66 are still living and 2 are extinct. Of the animals 

 245 are recent and 29 are extinct. Among the animals, the mollusks have 

 231 living and 7 extinct, while the insects have 7 extinct and 3 living, and the 

 mammals have 13 extinct and 8 living species. It will be noted that the in- 

 sects and the mammals, the highest and most complex types of the inverte- 

 brate and the vertebrate branches of the animal kingdom, have passed thru 

 the greatest changes during the postglacial period, the majority of the species 

 represented being extinct. The plants and the mollusks show little or no 

 change, the percentage of extinct species being very small. 



5. THE WABASH FAUNA 



Recently, Dr. O. P. Hay 230 proposed the name Wabash beds for the deposits 

 laid down subsequent to the retreat of the Wisconsin ice sheet, and to the biota 

 he gave the name of Wabash fauna, believing that the period between the 

 waning of the ice sheet and the historical period should bear a name and be 

 equivalent in value to the interglacial periods between the different ice sheets. 

 The proposed distinction seems appropriate, especially when considered in 

 relation to the insect and mammal faunas, which, as we have shown, contain 

 a large percentage of extinct species. The same relation between the plants 

 and the mollusks, and the insects and mammals continues thruout the inter- 

 glacial periods, the former consisting largely of species now living while the 

 latter are made up largely of species now extinct. 



Among the vertebrates, the fish and birds are too poorly represented to per- 

 mit of generalizations. Those species identified are all living. Of the mam- 

 mals it is to be noted that the megalonyx, peccary, extinct musk-ox and bison, 

 mastodon, two mammoths, two extinct elk (Cervalces), an extinct caribou, and 

 the giant beaver lived and roamed the territory left bare by the retreating 

 glacier for a long period after the ice had entirely disappeared from the Great 

 Lakes region, and it would be difficult indeed to declare with accuracy just 

 how recently some of these animals formed a part of the existing fauna (see 

 Chapter XII, page 371). 



™ Smith, Mis. Coll., No. 20, p. 13, 1912. 



