2O6 Bulletin American Museum of Natural History. [Vol. XXII, 



It is of interest to note that in a series of 25 male skulls one only 

 has a pair of well-developed upper canines, but another has a perfect 

 canine alveolus on one side, the tooth having fallen out; in the other 

 23 skulls there is not a trace or suggestion of even an alveolus at this 

 point. Still more exceptional is a single female skull, out of a series 

 of 25, with a pair of well-developed canines. 



Another erratic modification in the dentition is the reduction of the 

 posterior column on m 3 to a rudimentary condition, while in another 

 specimen m 3 on the left side has a well-developed supernumerary 

 column at the posterior border of the tooth, making four columns in- 

 stead of three, the corresponding tooth on the opposite side being 

 normal. Furthermore, the molars may have a well-developed acces- 

 sory column (5 mm. on m 3 ) or have no trace whatever of such a 

 feature. 



The following table of measurements gives the principal dimensions 

 of 6 adult male skulls and 6 skulls of adult females, and serves to show 

 the large amount of purely individual variation that may be expected 

 in any large series of deer skulls. Besides the considerable range in 

 size, the variation in certain parts is striking, especially in the form 

 and relative size of the nasal bones, in the length of the toothrow, 

 and in the upward extension of the premaxilla toward the nasals. 

 There is generally a vacuity between the upper border of the pre- 

 maxilla and the antero-lateral border of the nasal of the same side of 

 from 5 to 10 mm. in extent, but in a few specimens these parts are in 

 actual contact for a space of 2 to 15 mm. Every stage of gradation, 

 in different specimens, from extended contact (see Pll. xxi-xxvi 1 ) to 

 wide separation, is present. The differences in the form and relative 

 size of the nasals (see same Plates) , and the variation in the relation of 

 the premaxilla and maxilla to the nasals, would be of great importance 

 wherever occurring with constancy, but in the present series of deer 

 (and also in other species of deer), they are so inconstant, with every 

 stage of intergradation between the extreme conditions present, that 

 they are obviously to be regarded as due merely to individual differen- 

 tiation. With only the extreme phases of these differentiations 

 present, as might happen in the case of a small series of specimens, 

 and especially if the specimens came from different localities, or 



i Plates xxi-xxvi, Odocoileus sinalocz, 10 skulls, dorsal and lateral views of each, \ 

 natural size, as follows: 2 adult males, 4 adult females (in 4th year), and 4 young males (all in 

 3d year), to show individual variation in the size and shape of the nasals, in the size and shape 

 of the lachrymal fossa, and in the relation of the nasals to the maxilla and premaxilla. See also 

 Plate xxxi for further illustration of these variations in 8 young male skulls. 



