I08 KANSAS UNIVERSITY QUARTERLY. 



ing the internal side of bone beveled off to meet it somewhat as in 

 Ichihyodertcsznd Saurodon. The alveolar border is elongated and 

 supports three teeth and an empty alveolus for a fourth, all but 

 one of which are small. 



The maxilla is especially characterised by the manner in which it 

 unites with the premaxilla; instead of having the abrupt change to 

 the laminar portion in front of the posterior or palatine condyle, 

 found in A', aitdax, the bone is beveled off to a sharp anterior edge, 

 forming a reciprocal surface for the premaxilla. Both of the su- 

 perior condyles are small, the anterior one is directed well inward, 

 and the two are well separated from each other. In a paper re- 

 cently published by Professor Hay,* the author was inclined to the 

 opinion that the form of these condyles was of specific value in this 

 genus, giving as an illustration, the differences of these condyles in 

 the forms he refered to. A', nio/ossiis and X. thaumas. In this view 

 I must differ from him. I have examined the maxillae of a number 

 of specimens of this genus and seldom find two exactly alike; in 

 fact, the variation in this part are remarkably great, as would have 

 been apparent to Professor Hay in a larger series than he had at 

 command. The bone is quite deep at the palatine condyle, and the 

 superior border back of it presents a conspicuous groove, probably 

 for the attachment of the jugal. There are nineteen or twenty teeth 

 on one side and empty alveoli for several more, making a total of 

 about twenty-four. Back of the first six they all seem to be small. 

 Measurements: 



Premaxilla: length of alveolar border 62 mm 



" greatest depth of bone 90 " 



Maxilla: length of alveolar border 220 " 



'' depth at palatine condyle 835 " 



The dentary bones are short and deep, presenting thus a very ro- 

 bust appearance. They are much thickened at the symphysis, and 

 slope downward and backward nearly as much as in A'. lowii. The 

 alveolar border is short, and the teeth are few in number and are re- 

 markable for their large size anteriorly. The arrangement is: 

 three large, two small, one large, and twelve or thirteen medium 

 and small, making a total of nineteen or twenty in all. Many of the 

 posterior alveoli are empty, so that the size of the teeth contained 

 in them has to be estimated. In all probability the number and 

 size of the teeth varies with the individual, as in A', aiidax. The 

 articular portion is very similar to that of the species just men- 

 tioned. 

 *Zool. Bull. Vol. ii, No. 1. pp. ;34-a5, figs- 2-3. 



