Vol. XI, p. 143 



May 13, 1897 



PROCEEDINGS 



BIOLOGICAL SOCIETY OF WASHINGTON 



DESCRIPTION OF A NEW MUSKRAT FROM THE 

 GREAT DISMAL S^yAMP, VIRGINIA. 



BY Du. C. HART MERRIAM. 



Anions; the new mammals obtained at Lake Drummond, in 

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

 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. 



Tijpe from Lake Drummond, Dismal Swamp, Va. No. 75940, $ ad., 

 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, l)ut color very much 

 darker; incisor and molar teeth very much larger. 



Color. — Entire upper parts, abdomen, and S{)ot 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 i)ale 

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

 tipped with ]Yd\e dull fulvous. 



Cranial a)ul dental cliuracters. —Hknll 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 nnn. across cutting edges); molars much larger and heavier, the 

 upper series measuring about 16 mm. on crowns. 



BemarJcs.— 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 cliange cannot l)e determined from the material at 

 hand. 



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

 hind foot, 80. 



'A'i — Biol. So<;. Wash., Vi 



XI, 1S'J7 



(143) 



