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PLATE XII 



Upper molar teeth of Bison americanus and Bos taurus. (All natural size.) 



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Fio-. 1. Right upper molars, from above, of B. americanus (specimen No. 12). In this specimen the last 

 true molar is just through its alveolus, and the last pre-molar of the temporary set is about two thirds 



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grown ; the second true molar is still almost unworn. 



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Fio*. 2. Ei<:^ht upper molars, from above, of B. americanus, from a specimen (No. 100*) somewhat older 



than that represented in Fig. 1. . 



Fio-. 3. Riaht upper molars, from above, of B. americanus, from a specimen (No. 94) of the same age as 



that represented in Fig. 2. 

 Fi<T. 4. Eight upper molars, from above, of B. americanus, from a specimen (No. 11) somewhat older than 



those represented in Figs. 2 and 3. 

 Fig. 5. Right upper molars, from above, of B. americanus, from a specunen (No. 102), still older than 



that represented in Fig. 4. 

 Fig. 6. Rio-ht upper molars, from above, of B. americanus, from a specimen (No. 3940) still older than 



that represented in Fig. 5. 

 Fig. 7. Right upper molars, from above, of Bos taurus, from a specimen (No. 4500) corresponding in age 

 with the specimen of B. americanus represented in Fig. 1, the last pre-molar of the temporary set being 



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still in place. 

 Fig. 8. Right upper molars, from above, of Bos taurus, from a specimen (No. 4501) corresponding in age 



with the specimens of B. americanus represented in Figs. 2 and 3. 

 Fig. 9. Right upper molars, from above, of Bos taurus, from a specimen (No. 4) corresponding in age with 



the specimen of B. americanus represented in Fig. 4. 

 Fig. 10. Left upper molars, from above, of Bos taurus, from a specimen (No. 5003) a very little older 



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than the specimen represented in Fig. 9. 

 Fig. 11. Right upper molars, from above, of Bos taurus, from a specimen (No. 3) corresponding in age 



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with the specimen of B. americanus represented in Fig. 5. 



Fi<y. 12. Eight upper molars, from above, of Bos taurus, from a specimen (No., 2) corresponding in age 

 with the specimen of B. americanus represented in Fig. 6. 



Fig. 13. Second right upper molar, from Gardiner, Me., corresponding in age with the specimen repre- 

 sented in Fig. 12. The resemblance of this tooth to the corresponding tooth (second molar) of Bos 

 taurus, represented in Fig. 12, with which it is strictly comparable in age, is very close, while it differs 

 quite tangibly from the corresponding tooth of B, americanus represented in Fig. 6, with which it is 

 also strictly comparable in respect to age. (This specimen is one of the original lot found at Gardiner, 

 Me., and now belongs to the Boston Society of Natural History. It bears the following label : " Bison 



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* This specimen is the only one among a large series of skulls of Bison americanus ia whicli tlie crescents of enamel 

 of tlie first and second true molars have a prominent entering fold on their anterior and posterior borders, not, however, 

 exactly corresponding in this respect with the infolding seen in Bos taurus. The specimen, in every other respect, is 

 apparently normal. The specimen represented in Fig. 3 exactly correspontis in age with this, and illustrates the usual 

 form of the enamel crescents in B. americanus in specimens of this age. 



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