VOL. XI, p. 143 MAY 13, 1897 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



DESCRIPTION OF A NEW MUSKRAT FROM THE 

 GREAT DISMAL SWAMP, VIRGINIA. 



BY DR. C. HART MERRIAM. 



Among the new mammals obtained at Lake Drummond, in 

 the heart of the great Dismal Swamp, is a curious Muskrat. Jt 

 is by far the handsomest of the three forms thus far recognized 

 in the genus, and differs from them all in color and in the large 

 size of the teeth. 



Fiber macrodon sp. nov. 



Type from Lake Drummond, Dismal Swamp, Va. No. 75940, 9 a( L, 

 U. S. Nat. Mus., Biological Survey Coll. Collected Oct. 9, 1895, by Dr. 

 A. K. Fisher. Original No. 1788. 



General characters. Similar to Fiber zebethicus, but color very much 

 darker; incisor and molar teeth very much larger. 



Color. Entire upper parts, abdomen, and spot on chin blackish brown, 

 darkest and richest on back ; throat, sides of face, anterior part of breast 

 (to plane of fore legs), and inguinal region soiled whitish or very pale 

 drab, more or less tinged with pale fulvous; long hairs of sides and belly 

 tipped with pale dull fulvous. 



Cranial and dental characters. Skull similar to that of F. zebethicus, but 

 braincase more elongated posteriorly ; squamosal root of zygoma more 

 sloping (not standing out so squarely); incisors heavier (upper ones meas 

 uring 7.5 mm. across cutting edges); molars much larger and heavier, the 

 upper series measuring about 16 mm. on crowns. 



Remarks. The large teeth and remarkable color of the Lake Drum 

 mond Muskrat suffice to distinguish it at a glance. Whether or not there 

 is a seasonal color change cannot be determined from the material at 

 hand. 



Measurements. Type specimen: total length, 567; tail vertebrae, 244; 

 hind foot, 80. 



33 BIOL. Soc. WASH., VOL. XI, 181)7 (U3) 



