NOETHEKN FROGS 31 



enter the vast forest region, plant life as well as animal life 

 become more and more abundant and differentiated. In- 

 stead of the barren-ground caribou, we now meet with the 

 woodland form accompanied by another large ungulate, the 

 moose, while the flying squirrel, chipmunk, the ground 

 squirrel, woodchuck, white-footed mouse, musk-rat, beaver, 

 skunk, weasel, shrews, moles and many other beasts tenant 

 the forests, meadows, and banks of rivers.* 



A few amphibians, even, have succeeded in surviving the 

 rigours of the arctic winter of those regions, and have success- 

 fully established the most northern outposts in eastern North 

 America. The leopard frog (Eana pipiens), one of the 

 commonest as well as one of the most brilliantly coloured of 

 American frogs, is one of these. The pickerel (Eana palus- 

 tris), also the northern wood frog (Eana cantabrigiensis) 

 and the northern frog (Eana septentrionalis) have all been 

 observed in the neighbourhood of Hudson Bay. The most 

 interesting species is the swamp- tree frog (Chorophilus 

 nigritus), whose northern variety has advanced into this in- 

 hospitable region, though almost all of the other members 

 of the tree frog family (Hylidae) are typically southern 

 forms. f Whether newts occur in the Hudson Bay region is 

 not definitely known, but the salamander (Plethodon 

 cinereus), at any rate seems to have been met with. All these 

 species are peculiar to America. 



No reptiles have been noticed. The distribution of the 

 terrestrial mollusks, the snails and slugs, implies that an ad- 

 vance in a northward direction, similar to that recorded in 

 the case of mammals and amphibians, has taken place among 

 some groups of invertebrates. The typically American snails, 

 Polygyra monodon and Strobilops labyrinthica, have been 

 collected near Hudson Bay. 



When we analyse the constitution of all these western and 

 southern groups, and trace the relationship of the members 

 more carefully, we notice that many of them are not of 

 American ancestry. They all have lived, no doubt, long 

 enough in America to have become thoroughly established, 



* Preble, E. A., "Hudson Bay Region." 



t Dickerson, Mary 0., " The Frog Book," p. 158, 



