136 



THE DESEADO FORMATION OF PATAGONIA 



inclosed basin becomes a large pit. Between the posterior 

 lobe and the flaring cingulum on the posterior margin, 

 there is also a small posterior bay, which, in an old tooth, 

 will also appear as a pit, but being shallow, it does not 

 last long. 



The lower molars, as figured by Ameghino, are of the 

 same type as those of the toxodonts, consisting of two cres- 

 cents with the pillar in the middle of the posterior cres- 

 cent, but the crescents and pillar are very plump; so that 

 with wear they form broad grinding surfaces; and the 

 bays, instead of becoming pits, first appear as notches, 

 then disappear entirely. Each premolar and molar has a 

 cingulum on the internal and external sides. 



Fig. Q3. Premolar 4 to molar 3 — 1 / '2 natural size, after Ameghino. 



Measurements, Specimen 3179 



46 mm., width 50 mm. 

 51 mm., width 55 mm. 

 50 mm., width 51 mm. 



Upper dentition, molar 1, length 



Upper dentition, molar 2, length 



Upper dentition, molar 3, length 



Lower dentition, from Ameghino's measurements 



Lower dentition, premolar 4, length 



Lower dentition, molar 1, length 



Lower dentition, molar 2, length 



Lower dentition, molar 3, length 



28 mm., width 23 mm. 

 34 mm., width 24 mm. 

 46 mm., width 24 mm. 

 76 mm., width 23 mm. 



Only the distal end of the scapula has been found; and 

 this shows a shallow glenoid cavity, which is much longer 

 in the antero-posterior direction, than in the transverse. 

 The spine rises close above the rim of the glenoid, and is 

 unusually heavy. 



The lower half of the humerus is present, and character- 

 ized by very wide epi condyles, a shallow supratrochlear 

 fossa, a moderately deep anconeal fossa, no foramen, and 

 a wide shallow trochlea. The ulna, according to Gaudry, 

 is a long, heavy, nearly straight bone, with a shallow sig- 



