PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 63. 



The writer makes use furthermore of various indices based on 

 the measurements just mentioned. These are intended to show the 

 ratio between measurements of important parts in each skull and 

 to bring out the variations found in the different individuals. They 

 are to be employed also in determining the resemblances and the dif- 

 ferences between the various species. The record of these indices 

 forms Table 2. The numerals found in the second column on the left 

 side of the page refer to measurements correspondingly numbered 

 in Table 1. The basal length (measurement 2 of the latter table) is 

 valued at 100. 



Table 2. — Indices. 



1. Basallength in 4. 



2. Basal length in 6.. 



3. Basallength in 7.. 



4. Basal length in 11, 



5. Basal length in 12 



6. Basal length in 13 



7. Basal length in 14, 



8. Basal length in 15, 



9. Basal length in 17, 



10. Basal length in 19, 



11. Basallength in 27. 



12. Basal length in 31, 



13. Basal length in 32 



14. Basal length in 33, 



Bison occidentalis. 



Bison 

 bison. 



10541 



67 

 41 

 74 

 56 

 36 

 36 

 70 

 59 

 67 

 41 

 56 

 39 

 29 

 ISl 



10542 



70 

 46 

 72 

 54 

 36 

 36 

 70 

 60 

 70 

 41 

 55 

 37 

 28 

 181 



22374 



66 

 41 

 72 

 56 

 41 

 35 

 67 

 53 

 66 

 42 

 41 

 31 

 35 

 146 



Bison 

 alleni. 



7706 



59 

 41 

 72 

 50 

 36 

 34 

 55 

 51 

 59 

 38 

 77 

 34 

 27 

 210 



bonasus. 



67 

 43 

 71 

 50 

 36 

 38 

 64 

 55 

 67 

 40 

 48 

 31 

 28 

 159 



In this table the first three indices pertain to measurements which 

 lie in the median sagittal plane. These seem to show that no 

 important differences in longitudinal proportions exist among the 

 species B. occidentalis, B. bison., B. honasus, and B. alleni. Bison 

 alleni, however, seems to have a somewhat shorter brain-case; but 

 additional specimens are needed to prove this. 



The indices found in lines 4 to 10 are concerned with transverse 

 measurements and show, therefore, the relative widths of the skulls. 

 It w^ill be observed that there is no wide variation in the two skulls 

 of B. occidentalis; nor is B. bison far away. In line 8 the index is 

 53, but another individual at hand brings it up to 59. Bison bison 

 seems again to differ from both B. occidentalis and B. bonasus in 

 the greater width of the constriction on the maxillary ridge in front 

 of the orbit. This view is strengthened by another individual at 

 hand. 



It is to be noted that the indices of the widths in B. alleni are 

 always lower than the corresponding ones in B. occidentalis and 

 B. bison. An examination of the author's figure of this species == 



=" Proc. U. S. Nat. Mus., vol. 46, pi. 16, fig. 1. 



