348 University Geological Survey of Kansas. 



physis. The symphysis presents but one articular surface, which 

 is roughened, and does not have an extension of the tooth band 

 overhanging it. In these respects the jaw bears a superficial re- 

 semblance to that of some of the recent siluroids. The symphysis 

 is slightly deeper than wide. The tooth band is broadest at about 

 the center and narrowest at the posterior extremity, where the two 

 borders of the band are suddenly drawn inward. The teeth 

 continue over the side externally, and the whole band is inclined 

 inward toward the center and posterior extremity. The dental 

 pits are small, and densely packed in somewhat irregular longi- 

 tudinal rows, there being forty or more of these rows at the 

 broadest portion of the band, which is ten more than Cope 

 found in his specimen. The articular is more robust through- 

 out than in A. polymicrodus, and the form of the cotylus is dif- 

 ferent, for, instead of being partially supported on a shelf-like 

 expansion of bone, as in this species, it rests directly across the 

 main part of the articular. It is concave longitudinally, slightly 

 convex transversally, and is directed slightly backward instead 

 of forward, as in the species just mentioned. 



There is a small portion of a maxilla present, and also a frag- 

 ment of another bone, which is probably a palatine, although 

 it differs somewhat from tl\at of A. polymicrodus. The tooth 

 band of the maxilla seems to be more convex transversally than 

 in the species just mentioned, and there seems to be a total ab- 

 sence of the coarse striae which ornament the external and in- 

 ternal surfaces of the bone in this form. The supposed palatine 

 is a long and thin plate of bone which is covered with small 

 tooth pits on one side, which decrease in size toward one of the 

 extremities. At the end where the teeth are the largest there 

 is a projection which probably serves to bind the bone to some- 

 thing. 



Below are given the principal measurements of the mandible 



of our specimen and the one described by Professor Cope. 



Cope. k. u. 



Length of tooth band 150 mm. 165.0 mm. 



Depth of symphysis 16 " 19.5 " 



Width of symphysis 21.0 " 



