154 



MAURICE G. MEHL 



VENTRAL RIBS 



Weathered out about the specimen were many fragments of 

 ventral ribs. Several of these ribs have been restored and all show 

 a length of 260 mm. or more. Most of them are almost straight for 

 half their length, whence they curve gently to the extremity. At 

 the middle they are somewhat flattened, having greater and lesser 

 diameters of about 16 mm. and 12 mm. respectively. They taper 

 shghtly to the extremities and here the section is almost round. 

 These are probably lateral ribs of the ventral series. One of the 

 ribs differs considerably from the others in the amount of curvature. 

 It is broadly curved at the center with the extremities bent nearly 

 at right angles. This is possibly one of the median ventral series. 



COMPARISON or A. grandis and A. gracilis 

 A brief review of some of the salient features of these two 

 specimens will serve to show the distinctness of the two species: 



1. Terminal expansion of rostrum 

 taking place gradually and in- 

 creasing in width to the tip. 



2. Rostrum 94 mm. wide at a point 

 140 mm. in front of the antorbital 

 vacuity. 



3. Terminal expansion takes place in 

 front of third tooth.- 



4. Greatest length of skull is 

 977 mm. 



5. Length from anterior border of 

 orbits to tip of rostrum 755 mm. 



6. Interorbital width 68 mm. 



7. Terminal expansion of lower jaw 

 upturned along lateral margins to 

 form a median antero-posterior 

 grove. 



8. Rounded ridges along inner side 

 of alveoli prominent. 



9. Number of teeth in lower jaw 

 about 46 on each side. 



[o. Diameter of alveoli of lower jaw, 

 exclusive of the large anterior 

 ones, ranging between 8 mm. and 

 16 mm. 



1. Terminal expansion of rostrum 

 taking place suddenly and retain- 

 ing the same width to the tip. 



2. Rostrum 56 mm. wide at a point 

 140 mm. in front of the antorbital 

 vacuity. 



3. Terminal expansion takes place in 

 front of fifth tooth. 



4. Greatest length of skull is about 

 985 mm. 



5. Length from anterior border of 

 orbits to tip of rostrum 750 mm. 



6. Interorbital width 68 mm. 



7. Terminal expansion of lower jaw 

 in a plane. 



Rounded ridges along inner side 

 of alveoli not prominent. 

 Number of teeth in lower jaw at 

 least 49 on each side. 

 Diameter of alveoli of lower jaw, 

 exclusive of the large anterior 

 ones, ranging between 5 mm. and 

 8 mm. 



