New Specie* of Aplodontia. 311 



Hairs at base plumbeous. Hairs al base very dark plumbeous. 



Belly mouse-gray, strongly washed Rump and belly grizzled mouse- 



with dilute umber. gray, the latter sometimes faintly 



washed with very dilute brown. 



No distinct patch of white in anal A distinct patch of white in anal 



region. region. 



Cranial Characters. — The material before me consists of six- 

 teen skulls — eight of Aplodontia major and one of A. rufa from 

 my own collection, and seven of Aplodontia rufa from the U. S. 

 National Musenrn.* These skulls represent both sexes and va- 

 rious ages. Of the eight skulls of A. major, four are males and 

 four females. Of these, two of the males and three of the fe- 

 males are adults, there being two young males and one young fe- 

 male. Of the eight skulls of A. rufa, three (JSTos. 3891, 3942, 

 and 11358 U. S. Nat. Mus.) are fully adult— in fact old— and 

 they are doubtless males. The remaining five are more or less 

 immature and pertain to both sexes. Two of them are too much 

 broken to furnish complete tables of measurements. In the fol- 

 lowing comparisons, the skulls of adult males only are referred 

 to, unless the contrary is stated. 



Comparison of the skull of Aplodontia major with that of A. 

 rufa shows several points of difference, though none of much 

 taxonomic value. In absolute size A. mijor is much the larger. 

 The average of the basilar-length in the two adult males is 68.85 

 mm., and of the zygomatic breadth 62.35 mm. ; while the ave- 

 rage basilar-length in the three adult skulls of A. rufa is 64.20 

 mm., and the zygomatic breadth 55.66 mm. Coupled with this in- 

 crease in size, is a marked increase in the weight of the skullf 

 and in the development of its processes, ridges and muscular im- 

 pressions. While the skull of A. major has come to be much 



;: For the privilege of examining these specimens, I am indebted to Prof. 

 S. F. Baird, Director of the U. S. National Museum, and Mr. F. W. True, 

 Curator of Mammals. 



f The largest and heaviest skull of A. rufa that I have examined weighs 

 a little less than 16 grams, while the largest of A. major weighs nearly 24 

 grams. 



