EDENTATA OF THE SANTA CRUZ BEDS. 209 



MEASUREMENTS. 



Upper dentition, length 050 &-, width 007 



" " " -^6- 03 1 Lower dentition, length 041 



1 , length (z.^.antero-posterior diameter) .006 " " " ^ 027 



" width (/. e., transverse diameter) 005 y, length 005 



2-, length 006 " width 004 



" width 008 5 , length 007 



&, length 007 " width oog 



" width 009 -g, length 007 



A, length 007 " width 009 



" width 0085 f, length 009 



$-, length 005 5 " width 009 



The skull varies considerably in its appearance and proportions ; in the 

 more typical examples the skull is long and slender, with comparatively 

 narrow muzzle and palate ; the postorbital constriction is shallower and 

 more gradual than in H. longiceps, the forehead is narrower and the sagit- 

 tal crest on the frontals is lower and thicker ; the nasals are shorter in the 

 median line, but each has a very elongate lateral process which accom- 

 panies the maxillary to the edge of the anterior nares. The preorbital 

 fossa of the maxillary is quite shallow and the facial portion of that bone 

 is continued to an unusual distance in front of - as a thin plate ; the dor- 

 sal margin of this plate is strongly curved, making its vertical anterior 

 edge very short dorso-ventrally. The premaxillaries, as is shown by a 

 skull in the Ameghino collection, resemble those of H. longiceps in form, 

 but are much less elongate, the difference being principally in the anterior 

 branch, and the median notch in the palatine processes of the maxillaries 

 for the spines of the premaxillae is larger and more regularly U-shaped. 



The mandible differs in only a few details from that of H. longiceps ; 

 the predental beak is shorter and its dorsal border is much more nearly 

 horizontal and is lower with reference to the level of the teeth ; the sym- 

 physis is shorter and the profile of the chin rises more steeply, though 

 compared with most other species of the genus, the beak is very long. 

 The condyle is set upon a shorter neck than in H. longiceps and is thicker 

 and more convex ; the coronoid process is lower, wider, more erect and 

 less recurved, and the angular process is also shorter and wider and is less 

 distinctly inflected. The postero-external opening of the dental canal is 

 on the side of the ascending ramus. In the type-specimen the mental 

 foramen has a much more anterior position than in the other mandibles 

 referred to this species, but that is probably individual. 



