2 1 8 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. 



The teeth (Plates XXXIX, figs. 1-3, 5 ; XL, fig. 3) display consider- 

 able variation in size, as is apparent from the subjoined table of measure- 

 ments, but there is much less difference in form ; - 1 is small, recurved, 

 obliquely abraded, and of a compressed oval cross-section ; it is inserted 

 near the anterior edge of the maxillary, the palatine process of which 

 extends a short distance in front of it, while the facial portion extends 

 considerably farther, the diastema between - and - varies somewhat, but 

 is of about the same relative length as in most of the other species. The 

 molariform teeth are of rectangular or trapezoidal outline ; - is generally, 

 though not always rectangular, while ^ and - are trapezoidal, and - is 

 always much the smallest of the series ; the vertical grooving of these 

 teeth appears to be very capriciously present or absent. The two rows 

 of upper teeth may be either parallel, or, more commonly, slightly con- 

 vergent backward. Of the lower teeth, T is very small, erect and of 

 cylindrical or slightly oval form ; the diastema is short ; ^ and ? have the 

 ordinary rectangular shape and T is subcylindrical and somewhat irregular. 



MEASUREMENTS. 



No. 15,5^7. No. 15,011. No. 15,163. No. 15,545. 



Upper dentition, length 042 .043 -0435 .045 



" * 028 .028 .027 .028 



" ^ 036 .0375 .0375 .038 



J*-, length (i. e., antero-posterior diameter) .005 -O53 - OO SS S 



" width (i. e., transverse diameter) 004 .004 .004 -OO45 



, length 0055 -0053 -0055 .006 



" width 007 -0073 .007 .008 



&-, length 0065 .006 .006 .006 



" width 0085 .0085 -0075 .009 



A, length 006 .006 .005 5 .006 



" width 008 .008 .007 .0085 



5-, length 004 -0035 .003 .0045 



" width 0065 .006 .006 .006 



No. 15,507. No. 15,531. No. 15,155. 

 Lower dentition, length 036 .035 .037 



" TT 025 .0245 .024 



T , length 004 .005 .005 



" width 0043 .0045 .004 



j, length 0063 .007 .0065 



" width 0083 .009 .008 



y, length 0065 .007 .0063 



" width 0085 .0085 .008 



