SCOTT : LITOPTERNA OF THE SANTA CRUZ BEDS. 



39 



the posterior crescent." Such an association is ahnost certainly an acci- 

 dental one of Proter other ium or Licaphrmm with D. velox. 



For the mandibular dentition, I have two individuals, one the cast of 

 a jaw in the Ameghino collection, marked "co-type," the other (No. 

 15,295) in the Princeton collection. Between these two specimens there 

 are some striking differences, principally in the form of the caniniform 

 incisor and in the relative size of the molars. It may well be that we 

 have here to do with different species, but until more complete material 

 has been obtained, I shall prefer to consider the differences as sexual and 

 to regard the Princeton mandible as belonging to a female. 



In the co-type the caniniform Xz is broad and thin and the canine is 

 placed nearly midway between is and pr, while in the supposed female 

 the tusk is more slender and conical and very much less compressed, and 

 the canine is inserted somewhat nearer to is than to px. The grinding 

 teeth resemble those of the preceding species, except for their smaller size 

 and slightly greater relative width. Both of the mandibles indicate ani- 

 mals somewhat smaller than the type of the species. 



As will be noted from the table, the molars are considerably larger in 

 No. 15,295 than in the co-type. 



Measurements. 



Lower dentition, length . 

 Ij, greater diameter ; 



" lesser " ... 



Lower premolar-molar series, length 



" premolar series, length 

 Py, length (i. e., antero-posterior diameter) 



" width {i. e., transverse diameter) 



" width 





Pj, length 

 " width 





P^, length . 

 " width 





Lower molar series, length 





Mj, length . . . . 





" width . 





Mg-, length . 

 " width ... 





M^, length . 

 " width . 





o-iype. 



No. 



.096 



15,295- 



.007 



■oos 5 



.003 



.005 



.074 



■079 



•039 

 .005 



•039 

 .006 



.004 



.004 



.010 



.010 



.oos 



.005 



.011 



.011 



.008 



.008 



.on 



.011 



.010 



.010 



.036 



.041 



.0105 



.012 



.009 



.010 



.0115 



•013 



.009 



.010 



.012 



.015 



•007s 



.008 



