08 Mcrrlam — Preliiiiiaarij Synopfils of American Bears. 



definite limits beyond which it does not pass, and that excellent 

 and constant characters exist by which the several species and 

 subspecies may be recognized. 



Sexual difference in size is most conspicuous in the Grizzlies, 

 though it is marked in the Black bears also. In the latter the 

 disproportion is greater in the teeth than in the skull ; in the 

 female the molar teeth are much smaller, narrower, and less 

 massive than in the male. 



Individual variation in the teeth is the rule, and the amount 

 of this variation is surprising, affecting the number and relations 

 of the accessory cusps, and also the form and proportions of the 

 fourth upper and lower premolars, and the great posterior ' heel' 

 of the last upper molar. 



As is well known, the bears normally have 12 teeth, the dental 



lormula bemg 7— , c— -, P'^^^-> 



h 1 4 



-1= 1^ = 42. Tbe first three 



premolars above and l)elow, howe^'er, are small and nearly 

 functionless, and several of them usually fall out before the 



animal attains maturity, so that adult 

 skulls rarely contain more than 36 or 

 38 teeth. 



In the Grizzlies, Barren Ground, 

 Yakutat, and Kadiak bears the first 

 ^ lower molar (rn ,) has one or more 

 cusps or tubercles on the inner side 

 between tlie middle and posterior 

 cusps (fig. 6,'^), no trace of which 

 exists in the Black bears (fig. 6,'). 

 These intermediary cusps are absent 

 Fig. 6.-Lowercarnassiai tooth (wi) also iu the Sitka bear (fig. 6,1) In 

 and last premolar. |.j-^g Grizzlics and their allies the pos- 



z. B\ac^^hear{Ursusamer^canus). ^^j.^^^. (, (inner and OUtcr) are 



2. Sitka bear ( Utsus sitkensis). ^ 



^. Qr\zz\yh&&r{u,-stis hoiribiiis^. nearly oiDpositc ; in the Blacks they 



are more oblique. 

 Examination of the molar teeth in several hundred bear skulls 

 shows beyond question not only that the last upper molar de- 

 creases in size markedly (and probably rapidly) after the wear- 

 ing down of the crown has passed a certain plane, but also that 

 the length of tlie molariform series as a whole in both jaws 

 shortens materially. No ga])S are left between the teetli, the 

 wear being compensated 1)}^ a movement from behind forward 

 which keeps the crowns continually in contact. 



