MARYLAND GEOLOGICAL SURVEY 293 



as a rule, to an altitude of 1200 or 1300 feet. Above this, the whole 

 county, except the warmest slopes, which are tinged with Carolinian 

 forms, belongs to the Transition zone. In Garrett county, in the 

 upper part of the Transition zone (above 2600 feet altitude) cold 

 sphagnum and alder swamps abound. These swamps contain a strong 

 admixture of high Transition and even Boreal species, such as the 

 Junco, or Slate-colored Snowbird (Junco liyemalis), Solitary Yireo 

 (Vireo. soliiarius), Magnolia Warbler (Dendroica maculosa), 

 Canadian Warbler (Wilsonia canadensis), Kedbreasted Nuthatch 

 (Sitta canadensis), Hermit Thrush (Hylocichla aonalasclikae pattasii), 

 Redbacked Mouse (Evotomys gapperi), Canadian White-footed 

 Mouse (Peromyscus canadensis) , two species of Jumping Mouse, or 

 Jerboa (Zapus hudsonius and Z. insignis), Varying Hare (Lepus 

 americanus virginianus), and the northern Sooty Shrew (Sorex 

 fumeus), all of which were obtained by E. A. Preble at Finzel post- 

 office, six miles north of Frostburg. Still farther west the Boreal 

 tinge is even stronger, and in some very extensive swamps between 

 Accident and Bittinger (mainly on the west side of the wagon road) 

 Mr. Preble found spruce trees common. The cutting off of the 

 spruce and hemlock from these small boreal islands lets in the hot 

 sun and results, in numerous instances, in changing the fauna and 

 flora from Canadian to Alleghanian. 



The fauna of Allegany county is a mixture of Carolinian and Alle- 

 ghanian species and comprises, so far as known, no boreal islands. 

 The Potomac valley, and valleys of the principal streams, are Caro- 

 linian; the uplands, Alleghanian. 



