48 THE OSTEOLOGY AND MYOLOGY 



The molars have three roots:, corresponding to the three corners of the cro^^^^ ; two of 

 the roots are side by side, and external ; the third stands alone ; all are straight, slender 

 and nearly parallel ; each prong enters the alveolus by a distinct perforation of the bone. 

 The last molar has three roots like the others, but these are differently disposed. The 

 outer one stands alone, and is much larger than the other two, which are placed side by 

 side, though they still enter the alveolus by separate apertures. The surface of the tooth, 

 instead of being triangular, represents half an ellipse divided along its major axis ; the 

 curved border is postei'ior ; the straight one is nearly transverse, like the corresponding 

 anterior border of the preceding molars. The crown of this tooth presents an elevated rim 

 and a central depression, divided into two halves by a raised line that traverses the short 

 diameter. The inner and outer angles of the two parts have slightly developed cusps ; 

 the middle of the straight border rises in a small point. The surface represented by the 

 conjoined crowns of all the molars is but little convex in the longitudinal direction ; the 

 point of greatest convexity is at the penultimate molar, whence the curve sweeps rapidly 

 up past the last molar, and more gradually up along the anterior ones. The most ^iromi- 

 nent molar just reaches a line drawn from the tip of the canine to the apex of the paroc- 

 cipital. The grinding surface of the last molar looks directly downward ; that of the 

 others is more and more obliquel}^ bevelled from third to first, so that the grinding surface 

 of the conjoined molars is twisted upon itself. The transverse diameter of the upper 

 molars contrasts strongly with the narrowness of those of the lower jaw. (For vipper 

 teeth, see fig. 10 and fig. 11, p. 64.) ^ 



Lower Jaw. The four incisors on each side repeat the main characteristics of those of 

 the upper jaw, but the median pair are not noticeably longer than the rest, nor do they 

 stand apart from the others. These teeth are in close proximity to each other, but not 

 touching. The chief peculiarity is their great forward and outward inclination ; the an- 

 terior ones, in fact, are almost horizontal, instead of vertical. When the jaw is closed, the 

 four teeth are opposed to the interspaces between the four lateral upper incisors, falling 

 inside the line, and not reaching the median pair of the latter. 



The lower canine is smaller than the upper, but still of great size. It is inserted in 

 juxtaposition with the last incisor, and closes in front of, and inside of the upper canine, 

 in the wide space that occurs between the latter and the upper incisors. Its root is 

 longer than the exposed portion, much flattened, and inserted very obliquely in the bone. 

 The free portion is stout at the base, rapidly tapering to a sharp point, and much curved, 

 to bring the tooth into the vertical position from its very oblique line of insertion. As a 

 whole, the tooth is notably twisted upon its axis. It measures, in adult examples, neaily 

 an inch in length. 



The first premolar is situated midway in the wide interval between the canine and the 

 second premolar. This brings it directly under the upper first premolar, and leaves room 

 for the apex of the upper canine to descend between it and the lower canine. This tooth 

 repeats the characters of the corresponding upper one, but is still smaller. The second 

 is much the largest of the under premolars, but scarcely differs otherwise from the third, 

 with which it is in contact by a largely develoj^ed basal snag on the posterior border ; a 

 similar snag upon the third connects the latter with the first molar. These teeth close in 

 advance of the corresponding upper ones ; so that the second premolar passes by its pos- 

 terior border along the anterior border of the second upper one ; the latter is wedged 



