EUTRACHYTHERUS SPEGAZZINIANUS 



8l 



with a marked tendency to become vestigal. The suture 

 of the premaxilla comes to the base of inc. 3. There fol- 

 lows a short diastema, then a tiny alveolus for the canine, 

 closely followed by the first premolar which is also small. 

 The second premolar shows no inflexion. Beginning with 

 the third premolar there is a strong inner inflexion, which 

 in the fourth premolar and molars is bifurcated. The 

 molars are considerably larger than the premolars, the 

 second being the largest of the series. With each succes- 

 sive molar, the inflexion is wider, so that in m. 3 the tooth 

 is divided into three lobes of nearly equal size. All pre- 

 molars and molars are rootless, curved, and set so deep in 

 the jaw that they almost meet in the median line. A typi- 

 cal molar measures 50 mm. in length, of which only 7-8 



Fig. 48. E. spegazzinianus , right upper dentition natural size. 



mm. project above the border of the jaw. All the back 

 teeth are covered with a thick coating of cement. 



The arrangement of the teeth of the lower jaw is shown 

 in fig. 25 h., after Ameghino. The first and second incisors 

 are greatly enlarged. Incisor 3 is lacking, and the canine 

 vestigal. Pm. I is small and single-lobed, the succeeding 

 premolars and molars being large and divided into two lobes 

 by a deep external, and a shallow internal infolding. 



MEASUREMENTS 



Skull, width between the orbits 60 mm. 



Skull, width across the postorbital processes 88 mm. 



Skull, height from m. 2 to top of frontal 77 mm ' 



Skull, width of palate opposite inc. 2 

 Skull, width of palate opposite m. 2 



Dentition, 



Dentition, incisor I ant. post. 

 Dentition, pm. 3 

 Dentition, m. 2 

 6 



length inc. i to m. 3 

 length ii mm. 

 length II mm. 

 length 22 mm. 



42 mm. 



62 mm. 

 140 mm. 

 width 16 mm. 

 width 13 mm. 

 width 16 mm. 



