scott: toxodonta OF THE SANTA CRUZ beds. 
223 
As here regarded, this species is of medium size, horned in the male 
(A. ferum Amegh.) and hornless in the female and in the former the 
cranium is lower and wider and the zygomatic arches are much more ex- 
panded. A. magistev , as figured by Ameghino (’07, 70, fig. 9) differs so 
much from his specimen of A. ovinum (ibid., p. 73, fig. 10) in the form of 
the cranium and especially of the nasals, that it should perhaps be admitted 
as distinct, but, as already pointed out, dependence upon such characters 
would increase the number of species beyond all reasonable probability. 
As the description of the genus is drawn principally from individuals re- 
ferred to A. ovinum , it remains merely to give the dimensions. 
Upper dentition, length 
I 1 , length (i. e. ant. -post, diam.) 
“ width (i. e. transv. diam.) 
I-, length .... 
14 width .... 
I- 2 -, length .... 
44 width .... 
Upper canine, length 
4 4 4 4 width . 
Upper cheek-teeth series, length 
“ premolar series, length 
Pb length .... 
“ width .... 
Pb length .... 
“ width .... 
Pb length .... 
“ width .... 
P-, length .... 
“ width .... 
Upper molar series, length 
M 1 , length .... 
“ width .... 
Mb length .... 
“ width .... 
Mb length .... 
“ width .... 
Lower dentition, length 
I T , length 
Measurements. 
No. 15,131. 
•143 
•0055 
.008 
.013 
• -0135 
.005 
.004 
.006 
.004 
.096 
.041 
.0105 
.0105 
.011 
.0125 
.012 
.014 
•057 
.015 
.019 
.020 
.0205 
.028 
.019 
•135 
.006 
No. 15,118. 
.147 
.007 
.018 
.014 
.013 
.0045 
•0035 
.094 
•0435 
.008 
.006 
.0105 
.0115 
.012 
.012 
.013 
•oi55 
•0555 
.017 
.021 
.022 
•0235 
.026 
.021 
No. 15,136. 
.143 
.006 
No. 15,382. 
.0125 
.014 
.096 
.0405 
.006 
.006 
.011 
.014 
.013 
.016 
.059 
•0135 
.0215 
.020 
.024 
.030 
•0235 
No. 15,003. 
.051 
.016 
.017 
.019 
.0195 
.0225 
.017 
.124 
.004 
