224 U. Ss. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
polar bear. The premolars between this and the canines are either very small or wanting 
entirely in all the skulls of the grizzly, while in arctos there are two quite large ones. 
Corresponding differences exist in the lower molars, which are largest in the American bear, 
though not in the same proportion as the upper. The posterior molar is much more elongated 
in the grizzly, equalling the second in advance of it, while in UJ. arctos it is not more than 
three-fourths this length. An important difference exists in the fourth molar from behind. 
This in both exhibits one central and elevated compressed pointed lobe. In the grizzly, there 
is a tubercle at the base of this lobe postero-internally, from which a low angular ridge passes 
to the posterior end of the tooth, parallel with a similar ridge, passing back from the lobe 
and a little exterior to the middle line of the tooth. These two ridges meet behind and enclose 
a small valley. Now, in the U. arctos the inner tubercle with its ridge are wanting, and there 
only is a central ridge along the posterior half of the tooth. In this feature of a single ridge 
there is quite a close agreement with the Ursus americanus and cinnamoneus. The incisor teeth 
seem to have much the same characters in both species. 
In view of the very great difference in the size of the teeth in the smallest grizaly bear and 
the largest of our smaller species, it is hardly necessary to go into any detailed comparisons of 
the skulls of the species. The most important characteristics, independent of size, are to be found 
in the narrower head, straighter profile, and more flattened and concave forehead, greater pro- 
portional size of the posterior upper and lower molars, and numerous other features in the grizzly. 
The following table exhibits the detailed measurements and proportions of the skull in several 
grizzlies, from various localities, as well as of a skull of the polar bear: 
Measurements. 
] | 
Ursus horribilis. U. horribilis. U. horribilis, var. | U. maritimus. 
1218. 2037. jhorriaeus. 3 990. | 903. 
Monterey, Cal. || San Francisco. || Copper Mines. | N. Greenland. 
SKULL. | 
Inches. |100thsof}) Inches. |100ths of Inches. /100ths off Inches. |L00ths of 
length. length. length. length. 
| 
Total length ..--- Fotgdo nono scone ee soa ae 5a5 15.20 | 1.00 | 14.10 | 1.00 14.20 | 1.00 || 15.20 } 1.00 
From end of intermaxillary to end of condyle..---.-. 14.60 | .96 13.70 | .97 13,10 | .92 || 15.30} 1.01 
acetic aera 9.37| .61|| 7.20] .51] 8.20] -.58 |) 8.20] 54 
‘« height above base of cranium --.----------- 4.90 | .32 4.10 9} 4.40] .30 4,30] .28 
Distance between orbits .------------------------- 3.40 | .22 2.85 | .20 3.10} .21 8.637) 28 
ue a orbital processes_-..-.----------- 5.17 | .34 3.80 | .26 4.70 33 4.78 31 
NEEal Ones MeN EN sense wee ease Reese mews ceens| anes mene | tees S90 Sie |saeceee seer see 4.30 | 3:28 
width! before:—2-S2 cL S52). Soo ccte ete 1.40 09 1.30| .09) 1.40) .09 1.23 | .08 
Narrowest part of muzzle behind canines -.--------- 3.05 }| .20 8.10) } 21 2.80 | .19}) 3.48] .22 
Upper incisors, from front to molars ---.----------- 3.50 | .23 3.18 | .22 3.20 | .22 | 3.56] .23 
to hinder margin of palate ----.--.-- 7.80 | .51 7.00 | .49 6.95 | .48 | 7.80] .51 
width between external edges --..--- 2.06 sis 1.80 12 1. 87 13 2.00 13 
Upper molars, length taken together----------.---- 3.13 | .20 3.00} .21 2. 80 19 2.56 | .16 
least distance between -.-- .-..------ 2.05 13 1.80 | .12 | 1. 80 12 2.30 | .16 
From intermaxillary to end of nasals -...---------.|--------|------ GiS7"| -eah bee 7.20] .47 
U4 commencement of orbit. - ---- 6. 26 41 5. 60 39 5.70 | .40 5. 90 . 39 
Between post orbital points and occiput..--.-------- 8.70 | .57 7.80 | .55 7.80 | .54 8.60 | .56 
From post orbital points to end of nasals -.--------- 5.15 | .33 4.94 35 4. 64 32 6.00} .32 
end of intermaxillaries-..| 8. 00 52 || 7.40 52 || 7.40;] .53 7.90 | .&1 
