1869.] 315 [Cope. 



position in /. mii-tficus and I. Smockii. The terminal band-like area, 

 or what is in the longitudinal section the superior arched j^late, is 

 well developed, and ope^is along the outer inferior corner of the beak 

 for half its length. The beak itself is long and narrow, like that of 

 /. minficus. The inferior mai'gin is well curved inwards. The 

 outer side is concave above when in position, the masticatory face 

 overhanging a very little. The outer margin rises very little behind 

 the anterior dentinal area, and does not bear any dentinal area for 

 the length of the former behind it, where both specimens are broken. 

 The large inner area is very wide and oblique in transverse plane. 

 There is a small area — the end of a cylindrical column, just below the 

 inferior arched plate. 



Lines. 



Length to anterior margin anterior area 22 



Length of anterior area 8 



Width of jiosterior inner area 10.6 



Width of maxilla at middle above 14.8 



Width of maxilla at middle of beak 6 



Depth of maxilla at middle of beak 8.9 



Depth of maxilla anterior outer crest 18.8 



This sjjecies serves to connect the rather aberrant I. mirificus with 

 more usual forms. The specimens are a little smaller than those of 

 /. divaricatuii. 



Isehyodus divaricatus Cope. 



This species is represented by an inferior maxillary bone of the 

 right side in the Museum of the Academy, from the cretaceous marl 

 of Burlington Co., N. J. 



It indicates a species allied to the Iscliyodon mirificus (Edaphodon 

 mirificus Leidy, Proceed. Acad. Nat. Sci. Philadel., 1856, p. 221) and 

 of about the same size. The differences may thus be readily summed 

 up. The bone is less prolonged and attenuated at the apex ; the in- 

 ner or symphyseal margin, instead of presenting equal or less eleva- 

 tion than the outer, has a greater elevation ; and instead of being a 

 nearly straight line presents a thin angular expansion ; the outer mar- 

 gin has a corresponding concavity not seen in the known species. 

 In the latter, there is at this point a prominence above which is situ- 

 ated the anterior of the external tubercles; this projection is followed 

 by an open groove. Both the prominence and groove are wanting 

 in /. divaricatus. Both the external tubercles are smaller than in 

 I. mirificus, the anterior very much so, and Avith a round tbrm. The 

 internal is on the contrary very much larger, and anteriorly has an 



