64 
PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 
Pes, digit IV, terminal phalanx, width proximally 
“ “ V, first phalanx, length 
“ “ “ “ “ width proximally 
“ “ “ “ “ “ distally . 
“ “ “ second phalanx, length . 
“ “ “ “ “ width proximally 
“ “ “ “ “ “ distally 
“ “ “ terminal phalanx, length 
“ “ “ “ “ width proximally 
No. 
.003 
.0099 
.005 
.0035 
.006 
.004 
.003 
.007 
.003 
Interatherium extensum (Ameghino). 
(Pis. VI, Fig. 13 ; VIII, Figs. 3, 4, 1 7 , 18.) 
Icochilus extensus Amegh. ; Contrib. al Conoc., etc., pp. 471-472, PI. 15, 
figs. 4-9, 1889; Enum. Synoptique, etc., p. 15, 1894 (listed); Segundo 
Censo, etc., p. 150, 1898 (listed). 
Icochilus hegetothevoides Amegh.; Enum. Synoptique, etc., p. 17, 1894; 
Segundo Censo, etc., p. 15 1, 1898 (listed). 
Separated from /. robustum by characters of somewhat doubtful im- 
portance. The third upper incisor is frequently entirely wanting, or may 
be present on one side and absent on the other, and is much smaller than 
the corresponding tooth in I. robustum , which persists even in aged indi- 
viduals. In the best preserved specimen referred to /. extensum the 
fronto-nasal suture is straight, while in I. robustum it is curved. The 
absence of lyrate temporal ridges separates it from I. excavatum. 
Represented by two specimens in the Princeton collection No. 
15-041 
from a locality ten miles 
south of Coy Inlet and No. 15,666 from Coy 
Inlet. 
Measurements. 
No. 
No. 
15,04.1. 
15,666. 
Skull, length premaxillse to inion 
0815 
“ greatest width across arches 
b 
Cn 
OC 
“ interorbital width 
034 
“ least width of brain case 
0145 
“ width of palate at P- . 
0135 
.014 
“ width of palate at M-2 . 
.019 
.0185 
Upper dentition, length I-L-M- 2 - 
0435 
.0446 
“ “ “ Pi-Mi 
.029 
.0295 
“ “ “ Ml-Ml 
015 
•0155 
