Il8 KANSAS UNIVERSITY QUARTERLY. 



posterior extremity. It bears a tooth-band on the lower border 

 which is slightly concave longitudinally and in front where the 

 band is the broadest. Posteriorly the tooth-band gradually con- 

 tracts in width until the two borders come together at the posterior 

 end. The surface for the premaxilla is directed slightly inward, 

 and in some of the specimens it is slightly roughened for the liga- 

 ments binding the two bones together. Just back of this on the 

 superior border there is an elevated articular portion which serves 

 to bind the maxilla to the skull proper. It is rather rough above 

 and does not allow the free motion of the upper jaw found in some 

 of the other families of Physostomous fishes. Just back of this 

 there is a thin crest of boae extending backward over one-half the 

 length of the jaw. Both the external and internal sides of the 

 bone are covered with coarse longitudinal strise, the intensity of 

 which varies in different individuals. 



Measurements: 



Maxilla; length of tooth-band ii8 mm. 



Maxilla; height at posterior extremity 34 " 



Premaxilla; length 81 " 



Premaxilla; greatest height 375 '' 



The dentary has a tooth-band above covered with teeth very 

 similar to those on the parts described above. It is nearly flat in 

 front, but soon becomes directed downward internally, giving it a 

 somewhat beveled appearance which may be due to compression, 

 although it seems to occur in all of the specimens examined. The 

 band is broadest near the center and is overhanging externally and 

 in front. The symphysis is composed of two parts; an upper facet 

 which is directed inward and comes in contact with a correspond- 

 ing facet on the opposite side, and a lower one which is directed 

 forward and enters but little, if any, into the articulation of the two 

 jaws. At the symphysis the bones are shallow, but they soon 

 broaden and become very deep at the coronoid process. There 

 are very coarse ridges and grooves on both the external and in- 

 ternal sides. The articular extends well forward on the external 

 side and is united at the emargination of the dentary by an indis- 

 tinct suture. The cotylus is supported principally by a thick shelf 

 of bone extending inward from the main portion. It presents a 

 small concave facet which looks slightly forward, back of which 

 the angle is slightly curved and has been described by Cope as re- 

 sembling a boot with the toe inverted. 



