152 



PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



proportions, the rostrum and symphysial region of the mandible are nar- 

 rower and more pointed, and more or fewer of the anterior teeth tend to 

 .wear into horizontal instead of pyramidal grinding surfaces. This latter 

 feature, however, would appear to be less constant than Ameghino has 

 supposed. 



In the collection of the American Museum is a skull (No. 9230), appar- 

 ently referable to this species, from which the following dimensions have 



been taken. 



Measurements. 



Upper dentition, length il-m- 



I 



.178 



I5, major diameter 





.0113 



I-S-, major diameter 





.011 



" minor diameter 



.009 



" minor diameter 



. 



.010 



Lower canine, major diametei 



.013 



I-^, major diameter 



, 



.011 



" " minor diamete 



r . .011 



" minor diameter 



. 



.010 



Lower premolar series, length 



I . .071 



Upper canine, major 



diameter 



.012 



Py, length . 



.014 



" " minor 



diameter 



.011 



" width . 







.0105 



P-?-, length {i. e., ant. 



-post, diam.) 



.017 



Pj, length . 







.017 



" width {i. e., greatest trans, diam. 



) -0155 



" width . 







.010 



P^, length . 





.017 



P^, length . 







.019 



" width . 







.020 



" width . 







.011 



P4-, length . 







.017 



P^, length . 







.021 



" width . 







.022 



" width . 







.013 



Upper molar series, 



ength 





.058 



M3-, length . 







.020 



MA, length . 







.oi8 



" width . 







■013 



" width . 







.022 



Mj, length . 







.022 



M-^, length . 







.021 



M^, width . 







.014 



" width . 







.0225 



Skull, length in median basal 



line . .295 



M^, length . 







.021 



" " condyle to prm: 



<. . .317 



" width . 







.021 



" extreme length . 



•337 



ly, major diameter 







.008 



Cranium, length cond. to rim o 



f orbit .168 



" minor diameter 







.007 



Face, length orbit to premaxi' 



lary . .163 



1 2", major diameter 







.011 



Occiput, width at base . 



.081 



" minor diameter 







.0085 



Mandible, depth b 



elow 



Ps 



.038 



A fragmentary skeleton (No. 15,798) obtained by Mr. Hatcher at Lake 

 Pueyrredon may be provisionally referred to this species, with which it 

 agrees fairly well in size, but the diagnostic portions of the skull are 



wantmg. 



P^, length 



" width 



PA, length 



Measurements. 



.016 " width . 



.018 Mi, length . 



.0175 " width . 



.018 

 .018 

 .0205 



