274 



BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



of the subgenus Paraseiurus. The brain case is broad, high, and swol- 

 len, much as in Sciurus griseus anthonyl and & aberti. The frontals 

 are flattened, almost concave in front, but strongly bulging posteri- 

 orly. The postorbital processes are long and deflected. The interp- 

 terygoid fossa is long, as in the fox squirrel, measuring considerably 

 more in length than the combined lengths of the three upper true 

 molars. Incisive foramina long and narrow. Audital bullae large. 

 Greatest length of skull (type), 60 mm.; greatest breadth, 34. De- 

 tailed cranial measurements are given below: 



Cranial measurements of 8 specimens of Sciurus arizonensis. 



Locality. 



Fossil ('reek. Arizona 

 ....<lo 



.do 

 .do 



.do. 

 .do. 

 .do 



.do. 



£ i- 

 11 



65 

 61.4 

 64 

 61.9 



60. 5 

 63 



37 



37 



36. 5 



34.5 



35 



37.3 



mm. 



26. 5 



27. 2 



28. 2 

 27. .". 

 27. 6 

 26. 5 

 25. 5 



26 



mm. mm 



22 



21.3 



21 



21. V 



22 



21 



21 



20.8 

 22 



21.8 

 22. 1 



22 



21.5 



20 



21 



mm. mm 



9. 5 



9.5 

 9 



8. I 

 8.9 

 9.7 



31.7 



32 



33 



:;:; 



31.5 



31.2 



:;■ 



31.5 



" American Museum of Natural History. 



Habits and /on// distribution. — Each of the four squirrels inhab- 

 iting Arizona has its separate habitat, none being generally dis- 

 persed. The Mogollon chickaree is confined to the fir and spruce 



