PLATE XII. 



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



Fig. 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 

 grown ; the second true molar is still abnost unworn. 



Fig. 2. Right upper molars, from above, of B. americanus, from a specimen (No. 100*) somewhat older 

 than that represented in Fig. 1. 



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

 that represented in Fig. 2. 



Fig. 4. Right 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 specimen (No. 102), still older than 

 that represented in Fig. 4. 



Fig. 6. Right 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 

 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 ill Fig. 4. 



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

 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 

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



Fig. 12. Right 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 



* This specimen is the only one among a large series of skulls of Bison americanus in which the crescents of enamel 

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

 exactly corresponding in this respect witli the infolding seen iu Bus taurus. The specimen, in every other respect, is 

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

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



