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 almost 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) sodewhat 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 tawrus, 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 tawrus, 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 tawrus, 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 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 tawrus, The specimen, in every other respect, is 
apparently normal. The specimen represented in Fig. 3 exactly corresponds in age with this, and illustrates the usual 
form of the enamel crescents in B. americanus in specimens of this age. 
