432 



U. 8. P. R. R. EXP. AND 8URVEYS ZOOLOGY GENERAL REPORT. 



animal would be in strict accordance with the law of growth of mammals. As to the darker 

 colors of his smaller animal, they resemble almost exactly one of our largest specimens, (536,) 

 in which the fulvous of the sides is much obscured by black hairs. 



I find nothing in Dr. Harlan's description of Meriones microcephalus, which seems to indicate 

 a species different from the common one. 



Differences in the size of the ear has been considered to indicate two species. It must be 

 remembered, however, that a smaller specimen would naturally have a smaller ear ; and I have 

 not been able, in the extensive series before me, to realize any proportional differences in 

 different specimens. 



The following detailed measurement of a specimen in alcohol, from Pennsylvania, will show 

 the difference in size between it and a large skin collected in the Rocky Mountains by Captain 

 Beckwith : 



Measurements. 



Specimen in alcohol. * Dry skin ; somewhat defective. 



