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U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



preceding specimens, except that the main furrow is more in the centre, and the portion on 

 either side more nearly equal, including that covered and separated by the inner groove. The 

 color is also quite different, being everywhere of a uniform and rather bright reddish brown, a 

 little paler beneath. There is no darker wash along the back, where the hairs are very slightly 

 darker at the points, only appreciable on close examination. These are everywhere plumbeous 

 at base in marked contrast to their extremities. The feet, tail, and inside of cheek pouches, 

 are obscurely whitish. 



Among the specimens before me are three from Morgan county, Illinois, which exhibit a 

 coloration assigned by Audubon and Bachman to a particular season of the G. bursarius. In 

 these the body is of a dark plumbago color, deepest and very lustrous along the centre of the 

 back. Beneath, the plumbeous hairs are tipped with yellowish gray ; above, their extremities 

 are only a little darker. The hands and posterior portion of the arm are clear white, in strong 

 contrast to the surrounding fur. The bottom of the cheek pouches is also whitish. The tail 

 whitish, except the basal half above, which is plumbeous. 



The tail itself is long and well clothed with hair. The proportions of the limbs are not 

 materially different from what has been described in G. bursarius from St. Louis. They may 

 be a little smaller. The skull presents some differences : in a more deeply-grooved incisor ; the 

 centre of this groove a little nearer the inner edge ; a more slender zygomatic arch, the edges 

 of the zygomatic process of the upper maxillary being parallel, as viewed from above, instead of 

 widening considerably to embrace the end of the malar. The molar teeth are rather broader, 

 and the posterior lower one is nearly as wide as the one next to it. There is also a greater 

 dissimilarity between the two lobes of the anterior upper molar. The incisors are decidedly 

 thicker and more massive. If these differences are constant in many specimens, there will be 

 no danger in separating the lead-colored ones as distinct. 



Measurements. 



