HOLOCEPHALI. 135 



divergent from nearer origins. Inner face behind posterior exit 

 of apical column excavated, possibly for application of another 

 bone. Grinding face convex at middle, divided into two planes 

 behind, outer narrow and elevated, and inner oblique and sepa- 

 rated by an obtuse angle from excavation of inner side. Length 

 42 mm. (From Cope.) 



Formation and locality. Known only from the type described 

 above, from the "Greensand No. 5" [Hornerstown marl, K.] of 

 Hornerstown, N. J., and now in the American Museum at New 

 York. I have not seen this example. 



Genus ISOTJENIA Cope. 



Isotcenia Cope, Rep. U. S. Geol. Surv. Terr., II, 1875, p. 293. Type Isotcenia 

 neoccesariensis Cope, monotypic. 



Differs from Bdaphodon in lacking superior groove. Repre- 

 senting two anterior dentinal columns of the latter are two similar 

 exposures, both on same' plane and masticatory face together, 

 only separated by a narrow partition. 



A single species, extinct. 



ISOTCENIA NEOCCESARIENSIS Cope. 



Isotcenia neoccesariensis Cope, Rep. U. S. Geol. Surv. Terr., II, 1875, p. 293. 

 Hornerstoivn, N. J. Greensand No. 5. 

 Hussakof, Bull. Amer. Mus. Nat. Hist., XXV, 1908, p. 41, PI. 3, figs. 3-4 

 (type). 



Palatal with three solid planes, widest opposite to dentinal 

 columns and parallel, and nearly wide as latter. Lateral planes 

 not parallel. with one another, wider forms acute angle with last 

 described and narrower very obtuse angle so as nearly continuous 

 with same, running out into it posteriorly. More vertical side re- 

 tains same depth throughout. One end of bone rounded and 

 truncate, other end excavated directly at right angles to den- 

 tinal areas and then continued as an edentulous plate. Length 

 93 mm. ("From Cope.) 



Formation and locality. Known only from the above-described 

 type from "Greensand No. 5" [the Hornerstown marl, K.] at 



