EDENTATA OF THE SANTA CRUS BEDS. 



221 



alisphenoids, which usually cover the pterygoids on the outer side, but 

 sometimes leave a strip of the latter exposed. 



The mandible is fairly constant and characteristic, its principal variations 

 being in size and in the position of the postero-external opening of the 

 dental canal. The horizontal ramus is short, deep in the dentary region, 

 but relatively less thickened than in many of the species ; the predentary 

 beak is quite short and narrow, rapidly contracting to the rounded ante- 

 rior point; the profile of the chin is much steeper than in those species 

 which, like H. longiceps and H. indifferens, have very elongate rostra. 

 The ascending ramus is of the usual type ; the coronoid has but moderate 

 height and width and is less recurved than in H. indifferens ; the con- 

 dyle is small and set upon a relatively short neck, while the angular 

 process is long, extending well behind the plane of the condyle, and 

 dorso-ventrally broad, with the usual inflection. Typically, the external 

 dental foramen is placed upon the ascending ramus, near the anterior 

 margin and well above the base (see Plate XXXVII, Fig. i), but in some 

 instances it has a much more inferior position, approximating that which 

 Ameghino has employed to characterize Pseudhapahps (see Plate XL, 



Fig- 4)- 



In the following table No. I is the type specimen in the Ameghino col- 

 lection and No. 2 is a second individual in the same collection. 



MEASUREMENTS. 

 No. 

 i. 

 Skull, length in median basal line 



" " occipital condyle to anterior 



nares 136 



Cranium, length to anterior rim of orbit 



Face, length from orbit to anterior nares .... 



Occiput, height 039 



" width at base 



Cranium, width at postorbital constriction .... 



over lachrymals 



" height of parietal eminence 



Distance from occipital condyle to glenoid 



cavity 



Palate, length in median line 



" width at 1 



" " preorbital fossae 



No. No. No. No. No. 



2. 15,597- 15,545- I5,l(>0. 15,011. 

 .109 .113 .117 .112 



.137 



.038 

 .047 



.048 .047 .045 .048 



.020 "" JD22 .023 .021 



.043 .048 .048 .046 



.OI5 .OI9 .021 .Ol8 



O2O .022 .O2I .O2I 



