206 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



by the radically different manner of life. Scapula and pelvis are very 

 similar in the two groups, and even the limb-bones, notwithstanding their 

 very striking differences of proportions, have many features in common. 

 Even the feet, unlike as they at first appear, are yet so fundamentally 

 similar as to offer no difficulty to the assumption that the two groups were 

 derived from the same ancestral stock. 



HAPALOPS RECTANGULARIS Ameghino. 



(Plate XL, Figs, i, i.) 



Hapalops rectangularis Amegh. ; Enumeracion sistematica, etc., 1887, p. 22. 



Hapalops ellipticus Amegh.; Ibid. 



Schismotherium rectangularis Mercerat ; Rev. del. Mus. de La Plata, T. II. 



1891, p. 9. 

 Eucholceops ingens Lydekker, in part ; Anales del Mus. de La Plata, T. II, 



1894, p. 99. 



The type of this species, and therefore of the genus, is a small frag- 

 ment of the left mandibular ramus, in the La Plata Museum. Unfortu- 

 nately, this fragment is very uncharacteristic and might belong to any one 



FIG. 29. FIG. 30. 



Type of Hapalops rectangularis, x \. Type of Hapalops ellipticus, x \. 



La Plata Museum. La Plata Museum. 



of several species. In the collection made by Mr. Brown for the Ameri- 

 can Museum of Natural History is an excellently preserved mandible (No. 

 9222) with all of the teeth in place, which agrees very clearly with the 

 corresponding portion of the type and is probably referable, to the same 

 species. 



The first lower tooth is small, of compressed elliptical shape, with 

 oblique abraded surface, which presents forward and outward ; -2, which fol- 

 lows after a short diastema, is very broad and rectangular, with rounded 

 angles ; ^ is similar, but more distinctly quadrate, while T is of the usual, 

 subcylindrical shape. 



