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JOURNAL OF MAMMALOGY 
with black or blackish hairs the entire length; the metatarsal gland 
is longer in the mule deer; the antlers are larger in all proportions, 
with the primary divisions of the beam forking at a lesser angle, the 
anterior fork extending more nearly vertically to the plane of the 
occiput (less forward and inward). Cranially the mule deer differs 
from* the black-tail in that the post-frontal region arises distinctly 
Fig. 1. Diagrammatic Representation of Ancestry of Specimen Number 
223,685, U. S. National Museum, Biological Survey Collection 
B, Columbian black-tailed deer; M, mule deer; Hb hybrid from first cross; 
(specimen 223,685), hybrid from second cross; cf , male; 9 , female; X, crossed 
with. 
higher and more abruptly, producing in effect a more depressed in- 
terorbital region, whereas in the black-tail the superior aspect of the 
skull is comparatively flattened. There are other average differences 
between the two species, but in fully adult animals of comparable 
age the two forms seem to be sharply differentiated in each of the above 
characters, there being no overlapping, nor intermediates, in the nu- 
merous specimens examined. 
