52 THE DESEADO FORMATION OF PATAGONIA 



The two crescents are markedly separated by a cleft from 

 the external side of the tooth, opposite to which is a high 

 denticle, made by the fusion of the two ends of the cres- 

 cents where they come together. 



Proadianthus excavatus Ameghino 



P. excavatus. Amegh., loc. cit. above. 



The species is based on the two lower 

 premolars described above. I reproduce 

 the figure given by Ameghino. The 

 measurements are: length of pm. 3 and 



jrjjy 2 x. I^owcr right 



4, 10 mm.; height of mandible under pm. pm. 3 =ind 4— natural 



size, after Ameghino. 



4, 8 mm. 



