212 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. 



external opening of the dental canal is smaller and has a more inferior 

 position at the base of the ascending ramus. 



MEASUREMENTS. 



Lower dentition, length 042 ^ , length 008 



" " " -S? 0255 "width 008 



j, length (i. t., antero-posterior diameter) .0055 Mandible, length from condyle 125 



" width (i. e., transverse diameter) 005 



j, length 007 



" width 009 



y, length 0075 



" width 009 



" of predentary beak . . . .032 



" condyle to ^ 055 



" depth at ^ 029 



" thickness at -y 016 



height of condyle 040 



HAPALOPS ROBUSTUS Ameghino. 



Hapalops robustus Amegh. ; Rev. Argent, de Hist. Nat, T. I, 1891, p. 

 316. 



Typical examples of this species seem very distinct, but the grada- 

 tions are such that the propriety of separating it from H. indifferens is 

 doubtful. It is not represented by well preserved specimens in the New 

 York or the Princeton collection and I shall therefore quote Ameghino's 

 diagnoses of it. 



" Size a little greater than H. indifferens, but more robust ; distinguished 

 by the very broad palate, a little narrower in the middle than before or 

 behind ; - small and cylindrical, T subelliptical, with postero-external side 

 very broad and antero-external very narrow. Length of upper dental 

 series 53 mm., of lower 38 mm. ; breadth of palate at -, 16 mm. ; at -, 22 

 mm." ('91', 316). 



"Size a little smaller than H. indifferens (it was erroneously stated to 

 be a little larger in my description). The mandibular symphysis is shal- 

 low and very elongate ; the part which extends in front of the first tooth 

 is 35 mm. long. Length of skull from hinder edge of occipital condyles 

 to the anterior border of the maxillary 170 mm. The maxillaries are 

 prolonged in front of the first tooth more than in the other species ( 1 2 

 mm. on the palate)" (94", 145). 



The distinguishing feature of the skull is its great breadth, especially 

 in the facial region, and the depth of the preorbital fossae, which are shal- 

 low and ill defined in H. indifferens. In both species the molariform 

 teeth have similar rectangular shapes. 



