Fig. 113. Base of the skull—⅕ natural size; i.1,
incisor the right side grown over toward
the center as its mate is wanting;
i.2, incisor 2; Pal., palatinum;
Pt., pterygoid.

The lower jaws were associated with the above skull, and are complete to behind the third molars on both sides. They are very short and heavy, especially in the anterior portion, the symphysis extending back to opposite the middle of the second molar. The height under molar 3 is 150 mm. See frontispiece.

From the upper dentition, I give the measurements of my two chief specimens, together with those given by Ameghino for his type of P. sorondoi, and the figures given by Gaudry; from which may be seen the amount of variation which individuals may show.

Upper Dentition Specimen
No. 3207		 Specimen
No. 3250		 Ameghino’s
Type		 Gaudry’s
Specimen
Total length, inc. 1 to m. 3530 mm.
Inc. 1, length above alveolus133 mm.
Inc. 1, antero-posterior diam.49 mm.
Inc. 1, transverse diam.37 mm.42 mm.
Inc. 2, length above alveolus 174 mm.
Inc. 2, antero-posterior diam.59 mm.77 mm. 65 mm.
Inc. 2, transverse diam.40 mm.52 mm. 41 mm.
Premolar 2, length45 mm.52 mm.48 mm.40 mm.
Premolar 2, width36 mm.40 mm.30 mm.29 mm.
Premolar 3, length46 mm.49 mm.48 mm.40 mm.
Premolar 3, width57 mm.57 mm.46 mm.48 mm.
Premolar 4, length47 mm.51 mm.46 mm.43 mm.
Premolar 4, width63 mm.64 mm.58 mm.57 mm.
Molar 1, length55 mm.55 mm.57 mm.55 mm.
Molar 1, width68 mm.69 mm.61 mm.61 mm.
Molar 2, length68 mm.77 mm.70 mm.57 mm.
Molar 2, width85 mm.93 mm.75 mm.68 mm.
Molar 3, length75 mm.68 mm.83 mm.64 mm.
Molar 3, width86 mm.87 mm.82 mm.88 mm.

For the lower dentition, I give the figures which Ameghino records for his P. sorondoi, those given by Gaudry for his P. romeri, and the measurements of specimen No. 3207. The tushes in the lower jaw I would designate as incisors 2; because when the jaws are closed these diverge and their tips bite against the tips of the upper incisors 2. The first incisor seems to have been gradually lost and no space left for it in the front of the mandible, just as it was reduced and lost in the development from Moeritherium to Polymastodon or equivalent types.

Fig. 114. Lower dentition—⅕ natural size; edges of teeth
broken off in my specimen are indicated in outline.

Lower Dentition Specimen
No. 3207		 Ameghino’s
Type		 Gaudry’s
Specimen
Incisor 2 to molar 3, length510 mm.540 mm.‡415 mm.‡
Premolar 2 to molar 3, length325 mm.280 mm.272 mm.
Inc. 2, length above alveolus133 mm.188 mm.‡168 mm.‡
Inc. 2, antero-posterior diam.55 mm.60 mm.66 mm.
Inc. 2, transverse diam.40 mm.36 mm.44 mm.
Premolar 3, length46 mm.50 mm.54 mm.
Premolar 3, width36 mm.31 mm.35 mm.
Premolar 4, length55 mm.45 mm.50 mm.
Premolar 4, width46 mm.45 mm.47 mm.
Molar 1, length65 mm.50 mm.51 mm.
Molar 1, width59 mm.52 mm.54 mm.
Molar 2, length73 mm.56 mm.66 mm.
Molar 2, width73 mm.63 mm.66 mm.
Molar 3, length69 mm.67 mm.71 mm.
Molar 3, width74 mm.66 mm.69 mm.
‡ Figures taken from illustrations.

Four cervical vertebrae were preserved with the skull number 3207, of which only about a third of the atlas is represented, but fortunately we found a complete atlas isolated and of the same size. The measurements for the atlas are taken from this separate specimen. While my skull, especially the teeth, seems to have been larger than the skull Gaudry described, the cervicals are a little smaller. I give the measurements of the cervicals which we found, comparing them with the figures given by Gaudry.

Specimen
3344		 Gaudry’s
Specimen
Atlas, antero-posterior length (without hypophysis)120 mm.140 mm.
Atlas, greatest width304 mm.365 mm.
Atlas, height129 mm.140 mm.
Specimen
3207
Axis, antero-posterior length116 mm.124 mm.
Axis, greatest width223 mm.248 mm.
Axis, width of odontoid process96 mm.88 mm.
Axis, length of odontoid process48 mm.44 mm.
Cervical 3, length of centrum antero-posterior47 mm.45 mm.
Cervical 3, width of centrum125 mm.145 mm.
ervical 3, height of centrum105 mm.100 mm.
Cervical 3, width of neural canal75 mm.
Cervical 3, height of neural canal22 mm.
Cervical 4, length of centrum antero-posterior45 mm.
Cervical 4, width of centrum132 mm.
Cervical 4, height of centrum105 mm.