293 



MYL0GNATHU8, Leidy 



Proceediugs of the Academy of Philadelphia, 185G, 312. 



Mylognathus priscus, Leidy. 



Proceedings of the Academy of Philadelphia, 1856, 312 ; Transactions of the American Philo- 

 sophical Society, 1860, Plate. 



Fort Union Cretaceous of Long Lake, Nebraska. 



ISOTiENIA, Cope. 



Established on a maxillary bone, which differs from that of Ischyodus in 

 wanting the superior groove. Two dentinal columns are exposed, which rep- 

 resent the anterior two of that genus ; but they differ in being on the same 

 plane, and hence issuing on the masticatory face together, being only sepa- 

 rated by a narrow partition. Whether the other column is present is not 

 ascertainable, as the lower part of the bone is removed. 



IS0T.^NIA NEOCESARIENSIS, Cope. 



The solid planes of the maxillary bone of this species are three ; the 

 widest is opposite to the dentinal columns and parallel with them ; it is nearly 

 as wide as they. The lateral planes are not parallel with each other : the wider 

 forms an acute angle with the last described; the narrower, a very obtuse angle, 

 so as to be nearly continuous with the same, running out into it posteriorly. The 

 more vertical side retains the same depth throughout. One end of the bone 

 is rounded and truncate; the other is excavated directly at right angles to 

 the dentinal areee, and then continued as an edentulous plate, which is soon 

 broken off in the specimen. 



Measurements. 



Total length ^-"^^ 



Length of the dentinal columns "• "^^ 



Width of the dentinal columns ^.Va^ 



Depth on the vertical side 0. 020 



Greensaiid of New Jersey, No. 5, at Hornerstown ; John G. Miers. 

 SPHACEPCEA, Cope. 



Proceedings of the American Philosophical Society, 1869, p. 241. 

 SlMIAGEPCEA ACICULATA, Cope, /. C. 



Greensand of No 5, Birmingham, New Jersey. 



