EDENTATA OF THE SANTA CRUZ BEDS. 353 



MEASUREMENTS. 



Upper dentition, length 042 i, width 007 



1, length (i. e., antero-posterior diam- $-, length 008 



eter) 005 " width 007 



" width (i. e., transverse diameter). . . .0055 &, length 007 



S-, length 007 " width 005 



" width 005 Palate, width at 1 016 



3-, length 008 



In the succeeding measurements No. i is the type of N. lavagnanum 



in the La Plata Museum. 



No. i. No. 15,530. 



Lower dentition, length 040 .0385 



r , length 008 .008 



" width 005 .005 



j, length 0085 .008 



" width 006 .006 



3- length 009 .009 



" width 0065 .0065 



^, length 013 .0125 



" width 007 .006 



Width of jaw between -j .016 



" " " " Tf .010 



Mandible, depth at ? 0264 .026 



height of coronoid -59 



length of predental beak .037 



NEMATHERIUM AUCA (Ameghino). 



(Plate LXII, Figs, i, i", 6.) 



Lymodon auca Amegh.; Rev. Argent, de Hist. Nat; T. I, 1891, p. 324. 

 Lymodon perfectus Amegh. ; fenum. Synopt. des Mamm. Foss. de Pata- 



gonie; 1894, p. 166. 



The type of Lymodon aiica is an imperfect mandible and that of L. per- 

 fectus is the right half of the skull, with teeth ; the two specimens agree so 

 well that they might almost pertain to the same individual. This species 

 is one of the largest Santa Cruz representatives of the present family ; the 

 teeth are horizontally abraded, with some slight indications of bevelling 

 on one or more of them ; - is nearly cylindrical, though somewhat flat- 

 tened on the inner side ; -~- are very obscurely triangular, almost trape- 

 zoidal. In the mandible, T is triangular, with the apex behind ; ^ and ^ 

 are also triangular, but much compressed antero-posteriorly, broad trans- 



