152 MAURICE G. MEHL 



differs from that of A . grandis in that the upper surface is a plane 

 instead of being deeply grooved along the median hne. Below the 

 expansion there is a considerable convexity for the accommodation 

 of the roots of the large terminal teeth. Just back of the expansion 

 the mandible measures 29 mm. and has a thickness of about 17 mm. 

 Posteriorly the width increases gradually to 99 mm. at the pos- 

 terior end of the symphysis or about 9 mm. more than the same 

 measurement in A. grandis. It measures 25 mm. in thickness at 

 this point, while this measurement is 41 mm. in A. grandis. These 

 differences of measurement of the posterior end of the symphysis 

 may be partially due to crushing in the former specimen but there is 

 little evidence of this. Of the lower jaw none of the teeth is com- 

 plete; the few that remain are broken off close up to the mandible 

 and add little to our knowledge of the dentition except as to the 

 relative size and spacing of the teeth. The alveoli are all more or 

 less circular in outline but vary somewhat in size. In the expanded 

 portion of the anterior end are placed three large teeth of approxi- 

 mately equal sections. They are apparently antero-posteriorly 

 compressed, but this is probably an oblique section, a horizontal 

 section through an outward-directed tooth. The average antero- 

 posterior diameter is about 10 mm., considerably less than that of 

 A. grandis. The two anterior teeth are separated by a space of 

 24 mm., while the other teeth of the expanded portion are crowded 

 close together. The four teeth of the down-turned extremity of 

 the rostrum evidently met close in front of the lower mandible, 

 thus causing its large terminal teeth to close three on either side of 

 the rostrum. The alveoli immediately back of the expansion are 

 considerably smaller than the anterior ones and somewhat smaller 

 than the teeth in the same region of A. grandis. They average 

 about 5 mm. in diameter and are separated by a space of about 



6 mm. From 4 mm. they increase quite regularly to 8 mm. or 

 9 mm. in the posterior ones and all are approximately 6 mm. or 



7 mm. apart. In this species the teeth of the lower mandible are 

 more numerous than in A . grandis, about 49 on each side. 



THE VERTEBRAE 



The single vertebra freed from the matrix is a little distorted and 

 has lost the upper part of the spine but it shows the essential 



