66 
PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 
Fig. 12. 
Ameghino, determined by him as I. excavatum , shows this feature plainly. 
The dental characters given in the original description (Ameghino, 1889, 
pp. 472-473) have not been found to be of specific 
value. The third upper incisor is about as large as 
in /. extension. The posterior border of the nasals 
is curved, as in I. robustum. Characters of specific 
importance are exhibited by the atlas (PI. VIII, fig. 
28) in which the transverse processes are more 
sharply constricted proximally and less widely ex- 
panded distally. 
Represented by a crushed skull and mandible asso- 
ciated with the atlas and axis, the posterior portion of 
the vertebral column, the pelvis and portions of both 
hind limbs, No. 15,043, from a locality ten miles south 
of Coy Inlet. Several immature skulls also showing 
the lyrate crest are probably to be referred to this 
species. These are No. 9750 Am. Museum, No. 
15,291 and No. 15,146 from the same locality as No. 
I5.043- 
The adult individual (No. 15,043) is considerably crushed, so that only 
approximate dimensions can be given. 
Interatherium excava- 
tion, showing the lyrate 
crest, xf (No. 15,043). 
Slightly diagrammatic. 
Measurements. 
Length of skull ..... 
Interorbital width ..... 
Length of mandible including incisors 
Atlas, width across transverse processes 
“ width across anterior articular surface 
“ “ of neural arch 
“ “ “ inferior arch 
Axis, “ across condyles 
“ length of odontoid .... 
Fourteenth dorsal, length of centrum 
Fifteenth “ “ “ “ . . 
First lumbar 
Second “ “ “ . 
Third “ 
Fourth “ “ “ “ . . 
Fifth “ “ “ “ . . 
No. 
15,043. 
.080 
.0305 
.0665 
.025 
.0185 
.007 
.0045 
.017 
.004 
.0105 
.0105 
.01 1 
.0105 
.0115 
.0115 
.012 
