182 Preble New Species of Syrictptomys and Phenacomys. 



arch descending farther below level of top of skull; bullae more inflated. 



Measurements. Of type: total length, 130; tail vertebrae, 24; hind 

 foot, 18. The skull of the type measures: occipito-nasal length (tip of 

 nasals to foramen magnum), 26; zygomatic breadth, 16; interorbital con 

 striction, 3; length of upper molar series (crowns), 7. 



General remarks. Cranially Synaptomys bullata resembles closely S. 

 dalli of Alaska, but in color it shows much less reddish-brown than either 

 wrangeli or dalli. The hind foot of bullata is smaller than that of 

 wrangeli, dalli, or innuitus. 



Phenacomys mackenzii sp. nov. 



Type from Fort Smith, Slave River (near the Athabasca-Mackenzie 

 boundary line), Canada* Skin and skull No. 110,625, $ ad., U. S. Na 

 tional Museum, Biological Survey Collection. Collected June 29, 1901, 

 by Edward A. Preble and Alfred E. Preble. Original No. 4271 . 



General characters. Similar to Phenacomys celatus and P. c. crassus, 

 but differing in cranial characters. 



Color. Fur everywhere plumbeous at base, on back tipped with yel 

 lowish-brown, black, and gray in varying proportions; beneath grayish- 

 white, passing gradually on sides into color of back; tail bicolor, nar 

 rowly brownish above, grayish-white beneath. 



Cranial characters. Compared with skulls of P. celatus, those of 

 mackenzii have the bullaa more roundly inflated, palate shorter, rostrum 

 more slender, postorbital process of squamosal more slender, and in 

 terorbital constriction narrower. Interorbital beads prominent, even in 

 youth, converging early in life and nearly uniting in old age. 



Measurements The type measures: total length, 142; tail vertebras, 

 34; hind foot, 17. Ten adult specimens of both sexes from type locality 

 average: total length, 140.7; tail vertebrae, 32.7; hind foot, 17. 



General remarks. In color the type series resembles quite closely a 

 portion of the type series of Phenacomys c. crassus, kindly lent me for 

 comparison by Mr. Outram Bangs. I have not examined specimens of 

 Phenacomys constablei, described by Allen from Telegraph Creek, British 

 Columbia,* which seems to belong to this group, but its measurements 

 show that it has a larger hind foot than P. mackenzii. 



*Bull. Am. Mus. Nat. Hist., Vol. XII, p. 4, 1899. 



